On the detection of surface spin freezing in iron oxide nanoparticles and its long-term evolution under ambient oxidation.

Exchange bias (EB) effects linked to surface spin freezing (SSF) are commonly found in iron oxide nanoparticles, while signatures of SSF in low-field temperature-dependent magnetization curves have been much less frequently reported. Here, we present magnetic properties of dense assemblies of similar-sized (∼8 nm diameter) particles synthesized by a magnetite (sample S1) and a maghemite (sample S2) method, and the influence of long-term (4 year) sample aging under ambient conditions on these properties. The size of the EB field of the different sample (fresh or aged) states is found to correlate with (a) whether a low-temperature hump feature signaling the SSF transition is detected in out-of-phase ac susceptibility or zero-field-cooled (ZFC) dc magnetization recorded at low field and with (b) the prominence of irreversibility between FC and ZFC curves recorded at high field. Sample S1 displays a lower magnetization than S2, and it is in S1 where the largest SSF effects are found. These effects are significantly weakened by aging but remain larger than the SSF effects in S2, where the influence of aging is considerably smaller. A non-saturating component due to spin disorder in S1 also weakens with aging, accompanied by, we infer, an increase in the superspin and the radius of the ordered nanoparticle cores. X-ray diffraction and Mössbauer spectroscopy provide indication of maghemite-like stoichiometry in both aged samples as well as thicker disordered particle shells in aged-S1 relative to aged-S2 (crystallographically-disordered and spin-disordered according to diffraction and Mössbauer, respectively). The pronounced diminution in SSF effects with aging in S1 is attributed to a (long-term) transition, caused by ambient oxidation, from magnetite-like to maghemite-like stoichiometry, and a concomitant softening of the spin-disordered shell anisotropy. We assess the impact of this anisotropy on the nature of the blocking of the nanoparticle superspins.

Physical activity during pregnancy is associated with a lower prevalence of gestational diabetes mellitus in Vietnam.

AIMS: To assess the association between physical activity (PA) during pregnancy and the prevalence of gestational diabetes mellitus (GDM) accounting for sitting time. METHODS: The study used data from a cohort study of 2030 pregnant women in Vietnam. Women were recruited from six hospitals in Ha Noi, Hai Phong, and Ho Chi Minh City. Baseline measurements including PA and GDM were taken at 24-28 weeks of gestation. PA was assessed during the past 3 months before the interview using the interviewer-administered Pregnancy Physical Activity Questionnaire. GDM was diagnosed at 24-28 weeks of gestation using the 2013 World Health Organization criteria. RESULTS: 1987 out of 2030 pregnant women were included in the final analysis, of which 432 had GDM (21.7%). Women undertaking the highest level (upper tertile) of PA during pregnancy appeared to have a lower risk of GDM [odds ratio (OR) 0.70, 95% confidence interval (CI) 0.53-0.94, Ptrend 0.017] when compared to those at the lowest tertile of PA. Similarly, women with increased levels of moderate-intensive activity and household/caregiving activity during pregnancy were associated with reduced risks of GDM (OR 0.66, 95% CI 0.50-0.86, Ptrend 0.002 and OR 0.72, 95% CI 0.55-0.95, Ptrend 0.020, respectively). These apparent inverse associations were not attenuated by their sitting time. There were no significant associations between sitting time, light-intensity activity, vigorous-intensity activity, occupation, sports/exercise, commuting, or meeting exercise guidelines and GDM risk. CONCLUSIONS: High levels of PA, particularly moderate-intensity and household/caregiving activities during pregnancy were associated with a lower prevalence of GDM independent of sitting time.

Soyfood and isoflavone intake and risk of type 2 diabetes in Vietnamese adults.

BACKGROUND/OBJECTIVES: Animal studies have demonstrated that soy isoflavones exert antidiabetic effects. However, evidence regarding the association between soyfood intake, a unique source of isoflavones, and type 2 diabetes remains inconclusive. This study assessed the relationship between habitual intakes of soyfoods and major isoflavones and risk of type 2 diabetes in Vietnamese adults. SUBJECTS/METHODS: A hospital-based case-control study was conducted in Vietnam during 2013-2015. A total of 599 newly diagnosed diabetic cases (age 40-65 years) and 599 hospital-based controls, frequency matched by age and sex, were recruited in Hanoi, capital city of Vietnam. Information on frequency and quantity of soyfood and isoflavone intake, together with demographics, habitual diet and lifestyle characteristics, was obtained from direct interviews using a validated and reliable questionnaire. Unconditional logistic regression analyses were performed to examine the association between soy variables and type 2 diabetes risk. RESULTS: Higher intake of total soyfoods was significantly associated with a lower risk of type 2 diabetes; the adjusted odds ratio (OR) for the highest versus the lowest intake was 0.31 (95% confidence interval (CI): 0.21-0.46; P<0.001). An inverse dose-response relationship of similar magnitude was also observed for total isoflavone intake (OR: 0.35; 95% CI: 0.24 to 0.49; P<0.001). In addition, inverse associations of specific soyfoods (soy milk, tofu and mung bean sprout) and major isoflavones (daidzein, genistein and glycitein) with the type 2 diabetes risk were evident. CONCLUSIONS: Soyfood and isoflavone intake was associated with a lower type 2 diabetes risk in Vietnamese adults.

Superspin glass state in a diluted nanoparticle system stabilized by interparticle interactions mediated by an antiferromagnetic matrix.

In nanoparticle systems consisting of two magnetic materials (bi-magnetic nanoparticles or nanoparticles embedded in a magnetic matrix), there is a constantly growing interest in the investigation of the interplay between interparticle interactions and the nanoparticle-matrix interface exchange coupling, because of its enormous impact on a number of technological applications. The understanding of the mechanisms of such interplay is a great challenge, as it would allow controlling equilibrium and non-equilibrium magnetization dynamics of exchange coupled nanoparticles systems and finely tuning their anisotropy. Here, we provide evidence that this interplay leads to a collective superspin glass (SSG) behavior in a system of diluted ferromagnetic (FM) nanoparticles embedded in an antiferromagnetic (AFM) matrix (5% volume fraction of Co particles in Mn film matrix). We have developed a novel mesoscopic model to study the influence of interparticle interaction on the exchange bias (EB) and the dynamical behavior of assemblies of FM nanoparticles embedded in a granular AFM matrix. Our mesoscopic model is based on reducing the amount of simulated spins to the minimum number necessary to describe the magnetic structure of the system and introducing the adequate exchange parameters between the different spins. The model replicates remarkably well the observed static and dynamical SSG properties as well as the EB behavior. In addition, the proposed model well explains the role of the significant Co/Mn alloying and of the granularity of the matrix in mediating interparticle interactions through exchange and dipole-dipole coupling between the uncompensated moments of its grains and the exchange interaction at the Co/Mn interface.

Structure and magnetism in Cr-embedded Co nanoparticles.

We present the results of an investigation into the atomic structure and magnetism of 2 nm diameter Co nanoparticles embedded in an antiferromagnetic Cr matrix. The nanocomposite films used in this study were prepared by co-deposition directly from the gas phase, using a gas aggregation source for the Co nanoparticles and a molecular beam epitaxy (MBE) source for the Cr matrix material. Co K and Cr K edge extended x-ray absorption fine structure (EXAFS) experiments were performed in order to investigate atomic structure in the embedded nanoparticles and matrix respectively, while magnetism was investigated by means of a vibrating sample magnetometer. The atomic structure type of the Co nanoparticles is the same as that of the Cr matrix (bcc) although with a degree of disorder. The net Co moment per atom in the Co/Cr nanocomposite films is significantly reduced from the value for bulk Co, and decreases as the proportion of Co nanoparticles in the film is decreased; for the sample with the most dilute concentration of Co nanoparticles (4.9% by volume), the net Co moment was 0.25 µ B/atom. After field cooling to below 30 K all samples showed an exchange bias, which was largest for the most dilute sample. Both the structural and magnetic results point towards a degree of alloying at the nanoparticle/matrix interface, leading to a core/shell structure in the embedded nanoparticles consisting of an antiferromagnetic CoCr alloy shell surrounding a reduced ferromagnetic Co core.

Susceptibility losses in heating of magnetic core/shell nanoparticles for hyperthermia: a Monte Carlo study of shape and size effects.

Optimizing the heating properties of magnetic nanoparticles is of great importance for hyperthermia applications. Recent experimental results show that core/shell nanoparticles could give an increased specific absorption rate (SAR) compared to the magnetic oxide nanoparticles currently used. We have developed a modified phenomenological model based on the linear Néel-Brown relaxation model to calculate the SAR due to susceptibility losses in complex nanoparticles with ferromagnetic (FM) core/ferrimagnetic (FiM) shell morphology. We use the Monte Carlo (MC) simulation technique with the implementation of the Metropolis algorithm to investigate the effect of size and shape on the magnetisation behaviour of complex ferromagnetic/ferrimagnetic nanoparticles covered by a surfactant layer. The findings of our simulations are used as an input in our modified model for the calculation of the SAR. Our calculations show that for all the sizes and shapes the complex FM/FiM nanoparticles give higher SAR values than the pure ferrimagnetic ones due to their higher core saturation magnetisation. For all sizes the nanoparticles with the truncated cuboctahedral shape give the highest SAR values and the cubic ones the lowest ones. The decrease in the surfactant thickness results in an increase of the SAR values. Our results have the same characteristics as the available experimental data from Fe/Fe3O4 nanoparticles, confirming that the complex nanoparticles with core/shell morphology can optimise the heating properties for hyperthermia.

Consumption of a whey protein-enriched diet may prevent hepatic steatosis associated with weight gain in elderly women.

BACKGROUND AND AIMS: Protein consumption has been associated with cardio-metabolic benefits, including weight loss and improved insulin sensitivity, and may have potential benefits for individuals with fatty liver disease (FLD). We investigated the effect of increasing dietary protein intake from whey relative to carbohydrate on hepatic steatosis. METHODS AND RESULTS: A two-year randomized, double-blind, placebo-controlled trial of 30 g/day whey protein-supplemented beverage (protein) or an energy-matched low-protein high-carbohydrate beverage (control) for cardio-metabolic and bone health in 219 healthy elderly women, recruited from the Western Australian general population. Hepatic steatosis was quantified using computed tomographic liver-to-spleen (L/S) ratio. FLD was defined as liver-to-spleen difference <10 Hounsfield units. At baseline, FLD prevalence was 11.4%. Control and protein groups were similar in body mass index (BMI), insulin resistance, L/S ratio and FLD prevalence at baseline. At two-years, dietary protein increased by 20 g in the protein, but not the control, group. Total energy intake and physical activity remained similar between groups. At two-years, BMI and FLD prevalence increased in both groups, with no between group differences. L/S ratio increased in control, but not protein, group at two-years, with no between group differences. In a within group comparison, change in BMI correlated with changes in L/S ratio in control (r = 0.37, P = 0.0007), but not with protein group (r = 0.04, P = 0.73). CONCLUSION: Increasing dietary protein intake from whey relative to carbohydrate does not reduce weight, hepatic steatosis or the prevalence of FLD in elderly women. However, it may prevent worsening of hepatic steatosis associated with weight gain. CLINICAL TRIALS REGISTRATION: Australian New Zealand Clinical Trials Registry (Registration no. ACTRN012607000163404).

RECENT TRENDS IN GENDER RATIO AT BIRTH IN HANGZHOU, CHINA.

INTRODUCTION: Higher than normal sex ratios at birth in China have been reported since the early 1980's. This study aimed to investigate recent trends in sex ratio at birth in Hangzhou, capital of Zhejiang Province in southeast China. METHODS: Information on selected maternal and birth-related characteristics was extracted from the Hangzhou Birth Information Database for all pregnant women who delivered live births during 2005-2014. The sex ratios at birth were calculated after excluding infants with missing data on gender and those born with ambiguous genitalia. RESULTS: A total of 478,192 male births and 430,852 female births were recorded giving an overall ratio of 111.0. The sex ratio at birth was almost constant at around 110.7 during the period 2005-2008, followed by an increase to the peak at 113.1 in 2010 and then declined back to 109.6 in 2014. CONCLUSION: The gender ratio at birth in Hangzhou remained unbalanced for the past decade.

Fruit and vegetable consumption and risk of esophageal cancer: a case-control study in north-west China.

The north-western region of China carries a big burden of esophageal cancer with incidence above the national average. This study ascertained the association between fruit and vegetable consumption and the risk of esophageal cancer in this remote part of China. A case-control study was undertaken in Urumqi and Shihezi, Xinjiang Uyghur Autonomous Region of China, between 2008 and 2009. Participants were 359 incident esophageal cancer patients and 380 hospital-based controls. Information on habitual fruit and vegetable consumption was obtained by face-to-face interview using a validated semiquantitative food frequency questionnaire. Unconditional logistic regression analyses were performed to assess the strength of the associations. The esophageal cancer patients consumed significantly less fruits (mean 364.3, standard deviation [SD] 497.4 g) and vegetables (mean 711.4, SD 727.9 g) daily than their counterparts without the disease (mean 496.5, SD 634.4 g and mean 894.5, SD 746.1 g, respectively). The adjusted odds ratios were 0.48 (95% confidence interval 0.33-0.71) and 0.46 (95% confidence interval 0.32-0.68) for consuming at least 515 g of fruits and 940 g of vegetables per day, respectively, relative to at most 170 g and 520 g. With respect to nutrients contained in fruits and vegetables, intakes of vitamin C, vitamin E, ß-cryptoxanthin, potassium, and magnesium at high levels also reduced the esophageal cancer risk. In conclusion, inverse associations were evident between consumption of fruits and vegetables and the risk of esophageal cancer for adults residing in north-west China.

Structure and magnetism in Fe/FexPd1-x core/shell nanoparticles formed by alloying in Pd-embedded Fe nanoparticles.

We have investigated atomic structure and magnetism in Fe nanoparticles with a diameter of 2 nm embedded in a Pd matrix. The samples for these studies were prepared directly from the gas phase by co-deposition, using a gas aggregation source and an MBE-type source for the Fe nanoparticles and Pd matrix respectively. Extended absorption fine structure (EXAFS) measurements indicate that there is an appreciable degree of alloying at the nanoparticle/matrix interface; at dilute nanoparticle concentrations, more than half of the Fe atoms are alloyed with Pd. This leads to a core/shell structure in the embedded nanoparticles, with an FexPd1-x shell surrounding a reduced pure Fe core. Magnetism in the nanocomposite samples was probed by means of magnetometry measurements, which were interpreted in the light of their atomic structure. These point to a magnetized cloud of Pd atoms surrounding the embedded nanoparticles which is significantly larger than around single Fe atoms in Pd. The coercivities in the Fe/Pd nanocomposite samples are larger than in FexPd1-x atomic alloys of corresponding composition, which is consistent with exchange coupling between the magnetically harder and softer regions in the nanocomposite samples.

Under-reporting of energy intake in elderly Australian women is associated with a higher body mass index.

OBJECTIVES: Identify the extent of under-reporting of energy intake and the characteristics associated with implausible intakes in elderly women. DESIGN: Dietary intake was assessed using a 3-day weighed food record. Protein intake was validated by 24-hour urinary nitrogen. To examine under-reporting, participants were grouped according to their energy intake and compared to the Goldberg cut-off equation. Logistic regression was performed to assess the influence of body mass index (BMI) and social-demographic factors on under-reporting. SETTING: Community dwelling elderly women from Perth, Western Australia. PARTICIPANTS: 217 elderly women aged 70-80 years. RESULTS: Under-reporters had a higher physical activity level (p<0.001) compared with acceptable-reporters. The under-reporters also had a higher body weight (p=0.006), body mass index (BMI) (p=0.001), waist (p=0.011), hip circumference (p<0.001), whole body fat mass (p<0.001) and percentage body fat (p<0.001) than acceptable-reporters. Under-reporters had a significantly lower intakes of protein, fat, carbohydrate and alcohol (p<0.001) and fewer reported food items, compared with acceptable reporters. However, 24-hour urinary nitrogen was only marginally different between the two groups (p=0.053). Participants with a higher BMI were more likely to under-report their energy intake (BMI=25-29.9: odds ratio=2.98[95% CI=1.46-6.09]; BMI≥30: 5.84[2.41-14.14]). CONCLUSION: Under-reporting energy intake in elderly women was associated with a higher BMI, body fat and higher self-reported physical activity levels. A higher BMI (≥25) appears to be most significant factor in determining if elderly women will underreport their food intake and may be related to body image. These results have implications for undertaking surveys of food intake in elderly women.

GROWTH AND NUTRITIONAL STATUS OF THE FIRST SIX MONTHS OF LIFE AMONG SELECTED HOSPITALS--NAIROBI PROVINCE.

BACKGROUND: Exclusive breastfeeding for infants is recommended for the first six months for optimal health, development and growth. However, there is limited data on infant feeding practices and nutrition status of infants in Nairobi. OBJECTIVE: To assess infant growth and nutritional status and compare with feeding practices in the first six months of life in selected hospitals, Nairobi Province. DESIGN: Prospective cohort design SETTING: Five major hospitals in Nairobi namely; The Aga Khan, Pumwani Maternity, Mater Misercordiae, St Mary's Langata and Jamaa Hospitals. SUBJECTS: A sample of 692 mother-infant pairs were recruited at birth and followed up until six months. INTERVENTION: There was no direct experimental intervention, but there was observation of infant feeding practices, weight and height measurement was recorded every four weeks and determination of nutrition status of the infants for a period of six months. MAIN OUTCOME MEASURES: Nutritional status and infant feeding practices in the first six months. RESULTS: Slightly more than half (58.8%) of the mothers were formally employed and the rest were self employed. The mean age of the mothers was 28.3 ± 4.9 years. The mean income was KES 26,360 ± 34,696. The mean birth weight of infants was 3.24 ± 0.43 kg and 53.3% of all infants were male. Above 80% of infants were within normal weight based on weight for age Z-scores (WAZ) at 6, 10, 14 and 23 weeks. The prevalence of overweight based on WAZ was 9.5%, 11.6%, 11.9% and 11% at 6, 14, 19 and 23 weeks, respectively. There were no significant (P > 0.05) differences in WAZ between infants on different feeding methods. CONCLUSIONS: There was no significant difference in weight or length gain among children that were fully breastfed in comparison to those who were given infant formula or had mixed feeding. However, there was concern over the proportion of overweight infants, as the condition may lead to long term health problems.

A rare case of spontaneous thyroid cyst haemorrhage.

BACKGROUND: We report a case of hypopharyngeal swelling secondary to a spontaneous thyroid cyst haemorrhage. Haemorrhage is a known complication of thyroid cysts, and usually presents as external swelling and localised pain. CASE REPORT: A 93-year-old woman developed hypopharyngeal swelling, dysphagia and odynophagia. A computed tomography scan was consistent with thyroid cyst haemorrhage. The patient was treated with needle aspiration and intravenous steroid injections, with full recovery at thyroid clinic review. CONCLUSION: To our best knowledge, there has been no previous report of a hypopharyngeal swelling occurring secondary to spontaneous thyroid cyst haemorrhage. Our case is unusual because of the risk of airway compromise at the level of the hypopharynx, secondary to thyroid cyst haemorrhage.

Realizing high magnetic moments in fcc Fe nanoparticles through atomic structure stretch.

We describe the realization of a high moment state in fcc Fe nanoparticles through a controlled change in their atomic structure. Embedding Fe nanoparticles in a Cu(1-x)Au(x) matrix causes their atomic structure to switch from bcc to fcc. Extended x-ray absorption fine structure (EXAFS) measurements show that the structure in both the matrix and the Fe nanoparticles expands as the amount of Au in the matrix is increased, with the data indicating a tetragonal stretch in the Fe nanoparticles. The samples were prepared directly from the gas phase by co-deposition, using a gas aggregation source and MBE-type sources respectively for the nanoparticle and matrix materials. The structure change in the Fe nanoparticles is accompanied by a sharp increase in atomic magnetic moment, ultimately to values of ~2.5 ± 0.3 µ(B)/atom .

Mortality rate of alcoholic liver disease and risk of hospitalization for alcoholic liver cirrhosis, alcoholic hepatitis and alcoholic liver failure in Australia between 1993 and 2005.

BACKGROUND: Alcoholic liver disease (ALD) is an important contributor to the total burden of alcohol-related harm; however, the morbidity of different types of ALD in Australia has not been described. The aim of this study was to investigate recent trends in hospital admission rates among alcoholic liver cirrhosis, alcoholic hepatic failure and alcoholic hepatitis in Australia, as well as the mortality of ALD. METHOD: This is a population-based cohort study including the total 15+ years Australian population. Data were obtained from the Australian Bureau of Statistics and the Australian Institute of Health and Welfare. MAIN OUTCOME MEASURES: (i) trend of standardized mortality rates and trend of standardized hospital admission rates for males and females for 1993/1994-2004/2005 (fiscal year), (ii) relative risk of alcoholic liver cirrhosis, alcoholic hepatic failure and alcoholic hepatitis hospital admissions for 1999/2000-2004/2005. RESULTS: The mortality rate of ALD decreased significantly. Significant increases in hospital admissions for alcoholic hepatic failure among older adults and alcoholic hepatitis among younger age groups were observed. There is a significant 10-fold increase in the risk of hospital admissions of alcoholic cirrhosis in 2002/2003 for the 20-29 years population. CONCLUSION: Reductions in overall ALD mortality observed are likely the result of advances in disease management. Significant increase in hospital admissions suggests an increase in the prevalence of ALD among the Australian population. Dramatic increases in hospital admissions for alcoholic cirrhosis in 2002/2003 for the 20-29 years population may have been due to an increase in screening of alcohol-related harms in primary care settings.

The effectiveness of health promotion materials and activities on breastfeeding outcomes.

AIM: To determine the effect of mothers receiving health promotion material and education antenatally and/or postnatally on breastfeeding outcomes in Perth, Western Australia. METHODS: A 12-month longitudinal study was conducted in two public maternity hospitals in Perth, Western Australia, between 2002 and 2003. Data were collected on a consecutive sample 587 mothers. RESULTS: The results showed that mothers who received an individual consultation or were involved in a discussion on breastfeeding antenatally with hospital staff were approximately 55% less likely to cease fully breastfeeding (HR 0.44; 95% CI 0.24-0.88) before 6 months, and 50% less likely to cease any breastfeeding before 12 months postnatally (HR 0.51; 95% CI 0.28-0.92). In the postnatal period, mothers who received instruction on positioning and attachment of the infant to the breast while in hospital were approximately 30% less likely to cease fully breastfeeding before 6 months (HR 0.66; 95% CI 0.45-0.99). CONCLUSION: The results of this study suggest a positive association between receiving individualized breastfeeding information in both the antenatal and postnatal period, and breastfeeding outcomes.

Hepatitis B and breastfeeding in Hangzhou, Zhejiang Province, People's Republic of China.

OBJECTIVE: This study examined infant feeding methods in hepatitis B-positive mothers in Zhejiang Province, People's Republic of China. METHODS: A cohort study was undertaken in Hangzhou in Zhejiang Province. A sample of 638 mothers was recruited at birth from the city of Hangzhou and was followed up until their infants were 6 months of age. RESULTS: Chronic hepatitis B is a continuing public health issue in pregnant women. Breastfeeding is the foundation of infant nutrition, sets the scene for lifetime health, and is important for all mothers. In the Hangzhou cohort of 638 mothers, 38 were identified as hepatitis B positive, a rate of 6.0%. All of the infants of the hepatitis B-positive mothers were fed on formula immediately after birth while their breastmilk was tested for virus transmission and their infants were vaccinated. At 1 month of age 61.8% of the hepatitis B-positive mothers were breastfeeding compared to 92% of the remainder of the cohort. The rates at 3 months were 60.6% and 89% and at 6 months were 45.5% and 64%, respectively. The hazard ratio for hepatitis B-positive mothers discontinuing breastfeeding before 6 months was 3.69 (95% confidence interval, 2.28, 5.98). CONCLUSIONS: The World Health Organization recommends that all mothers who are hepatitis B positive breastfeed their infants and that their infants be immunized at birth. In this study breastfeeding rates of hepatitis B-positive mothers were substantially less than those of the other mothers.

Probing atomic structure in magnetic core/shell nanoparticles using synchrotron radiation.

Core/shell Fe/Cu and Fe/Au nanoparticles were prepared directly by deposition from the gas phase. A detailed study of the atomic structure in both the cores and shells of the nanoparticles was undertaken by means of extended absorption fine structure (EXAFS) measurements. For Fe/Cu nanoparticles, a Cu shell ∼ 20 monolayers thick appears similar in structure to bulk Cu and is sufficient to cause the structure in the Fe core to switch from body centred cubic (bcc; as in bulk Fe) to face centred cubic. This is not the case for thinner Cu shells, 1-2 monolayers in thickness, in which there is a considerable contraction in nearest-neighbour interatomic distance as the shell structure changes to bcc. In Fe/Au nanoparticles, the crystal structure in the Fe core remains bcc for all Au thicknesses although there is some stretching of the lattice. In thin Au shells ∼ 2 monolayers thick, there is strong contraction in interatomic distances. There does not appear to be significant alloying at the Fe/Au interface.

Interface exchange coupling in Co nanoparticles dispersed in a Mn matrix.

The structural and magnetic properties of 1.8 nm Co particles dispersed in a Mn matrix by co-depositing pre-formed mass-selected Co clusters with an atomic vapour of Mn onto a common substrate have been studied by using EXAFS (extended x-ray absorption fine structure), XMCD (x-ray magnetic circular dichroism), magnetometry, and theoretical modelling. At low Co volume fraction (5%) Co@Mn shows a significant degree of alloying and the well-defined particles originally deposited become centres of high Co concentration CoMn alloy that evolves from pure Co at the nanoparticle centre to the pure Mn matrix within a few nm. Each inhomogeneity is a core-shell particle with a Co-rich ferromagnetic core in contact with a Co-depleted antiferromagnetic shell. The XMCD reveals that the Co moment localized on the Co atoms within the Co-rich cores is much smaller than the ferromagnetic moment of the Co nanoparticles deposited at the same volume fraction in Ag. Electronic structure calculations indicate that the small magnitude of the core Co moment can be understood only if significant alloying occurs. Monte Carlo modelling replicates the exchange bias (EB) behaviour observed at low temperature from magnetometry measurements. We ascribe EB to the interaction between the ferromagnetic Co-rich cores and the antiferromagnetic Mn-rich shells.