Magnon-Phonon Coupling of Synthetic Antiferromagnets in a Surface Acoustic Wave Cavity Resonator.

We used a surface acoustic wave (SAW) cavity resonator to study the coupling of acoustic magnons in a synthetic antiferromagnet (SAF) and phonons carried by SAWs. The SAF is composed of a CoFeB/Ru/CoFeB trilayer, and the scattering matrix of the SAW resonator is studied to assess the coupling. We find that the spectral line width of the SAW resonator is modulated when the frequency of the excited magnons approaches the SAW resonance frequency. Such a change in the spectral linewidth can be well reproduced using macrospin-like model calculations. From the model analyses, we estimate the magnon-phonon coupling strength to be ∼9.9 MHz at a SAW resonance frequency of 1.8 GHz: the corresponding magnomechanical cooperativity is ∼0.66. As the spectral shape hardly changes in a CoFeB single-layer reference sample, these results show that SAF provides an ideal platform to study magnon-phonon coupling in an SAW cavity resonator.

Research Activities in Materials Science and Engineering with Academic-Industrial Alliances during the COVID-19 Pandemic.

During the COVID 19 pandemic, the importance of global academia-industrial alliances has increased. It is hoped that the alliances will help us to solve the current problems caused by the pandemic. In this paper, we introduce the application of IT tools and communication skills utilized in a special educational project for an academia-industrial collaboration. Some concrete examples from 2020 are provided from the viewpoint of the national alliance project in Japan. A discussion is included that describes the plans available to increase and strengthen the national project in the future.

Switchable generation of azimuthally- and radially-polarized terahertz beams from a spintronic terahertz emitter.

We propose and demonstrate a method of generating two fundamental terahertz cylindrical vector beams (THz-CVBs), namely the azimuthally- and radially-polarized THz pulses, from a spintronic THz emitter. We begin by presenting that the spintronic emitter generates the HE21 mode, a quadrupole like polarization distribution, when placed between two magnets with opposing polarity. By providing an appropriate mode conversion using a triangular Si prism, we show both from experiment and numerical calculation that we obtain azimuthal and radial THz vector beams. The proposed method facilitates the access of CVBs and paves the way toward sophisticated polarization control in the THz regime.

Acoustic spin Hall effect in strong spin-orbit metals.

We report on the observation of the acoustic spin Hall effect that facilitates lattice motion-induced spin current via spin-orbit interaction (SOI). Under excitation of surface acoustic wave (SAW), we find that a spin current flows orthogonal to the SAW propagation in nonmagnetic metals (NMs). The acoustic spin Hall effect manifests itself in a field-dependent acoustic voltage in NM/ferromagnetic metal bilayers. The acoustic voltage takes a maximum when the NM layer thickness is close to its spin diffusion length, vanishes for NM layers with weak SOI, and increases linearly with the SAW frequency. To account for these results, we find that the spin current must scale with the SOI and the time derivative of the lattice displacement. These results, which imply the strong coupling of electron spins with rotating lattices via the SOI, show the potential of lattice dynamics to supply spin current in strong spin-orbit metals.

Current-Induced Modulation of the Interfacial Dzyaloshinskii-Moriya Interaction.

The Dzyaloshinskii-Moriya (DM) interaction is an antisymmetric exchange interaction that is responsible for the emergence of chiral magnetism. The origin of the DM interaction, however, remains to be identified albeit the large number of studies reported on related effects. It has been recently suggested that the DM interaction is equivalent to an equilibrium spin current density originating from spin-orbit coupling, an effect referred to as the spin Doppler effect. The model predicts that the DM interaction can be controlled by spin current injected externally. Here we show that the DM exchange constant (D) in W/CoFeB-based heterostructures can be modulated with external current passed along the film plane. At higher current, D decreases with increasing current, which we infer is partly due to the adiabatic spin transfer torque. At lower current, D increases linearly with current regardless of the polarity of current flow. The rate of increase in D with the current density agrees with that predicted by the model based on the spin Doppler effect. These results imply that the DM interaction at the heavy-metal-ferromagnetic-metal interface partly originates from an equilibrium interface spin (polarized) current which can be modulated externally.

Period of a comblike pattern controlled by atom supply and noise.

Pattern formation of a step on a growing crystal surface induced by a straight line source of atoms, which is escaping from the step at a velocity V(p), is studied with the use of a phase field model. From a straight step, fluctuations of the most unstable wavelength λ(max) grow. Competition of intrusions leads to coarsening of the pattern, and survived intrusions grow exponentially. With sufficient strength of the crystal anisotropy, a regular comblike pattern appears. This peculiar step pattern is similar to that observed on a Ga-deposited Si(111) surface. The final period of the intrusions, Λ, is determined when the exponential growth ends. The period depends on the strength F(u) of a current noise in diffusion as Λ∼λ(max)|lnF(u)|: such a logarithmic dependence is confirmed for the first time. A nonmonotonic V(p) dependence of Λ indicates that the comblike pattern with a small V(p) is related to an unstable growth mode of the free needle growth in a channel. The pattern is stabilized by the guiding linear source.

A meta-analysis of (18)F-Fluoride positron emission tomography for assessment of metastatic bone tumor.

PURPOSE: The aim of this study was to assess the diagnostic performance of (18)F-Fluoride positron emission tomography (PET) or positron emission tomography/computed tomography (PET/CT) compared with bone scintigraphy (BS) planar or BS planar and single photon emission computed tomography (SPECT) in evaluating patients with metastatic bone tumor. MATERIALS AND METHODS: We performed a meta-analysis of all available studies addressing the diagnostic accuracy of (18)F-Fluoride PET, (18)F-Fluoride PET/CT, BS planar, and BS planar and SPECT for detecting the metastatic bone tumor. We determined sensitivities and specificities across studies, calculated positive and negative likelihood ratios, and drew summary receiver operating characteristic curves using hierarchical regression models. We also compared the effective dose and cost-effectiveness estimated by data from the enrolled studies between (18)F-Fluoride PET or PET/CT and BS planar or BS planar and SPECT. RESULTS: When comparing all studies with data on (18)F-Fluoride PET or PET/CT, sensitivity and specificity were 96.2% [95% confidence interval (CI) 93.5-98.9%] and 98.5% (95% CI 97.0-100%), respectively, on a patient basis and 96.9% (95% CI 95.9-98.0%) and 98.0% (95% CI 97.1-98.9%), respectively, on a lesion basis. The Az values of (18)F-Fluoride PET or PET/CT were 0.986 for the patient basis and 0.905 for the lesion basis, whereas those of BS or BS and SPECT were 0.866 for the patient basis and 0.854 for the lesion basis. However, the estimated effective dose and average cost-effective ratio were poorer for (18)F-Fluoride PET or PET/CT than those of BS planar or BS planar and SPECT. CONCLUSION: (18)F-Fluoride PET or PET/CT has excellent diagnostic performance for the detection of metastatic bone tumor, but the estimated effective dose and average cost-effective ratio are at a disadvantage compared with BS planar or BS planar and SPECT.

18F-fluoride uptake in bone metastasis: morphologic and metabolic analysis on integrated PET/CT.

OBJECTIVE: The aim of our study was to evaluate detectability of bone metastatic lesions and evaluate the correlation between (18)F-fluoride uptake patterns on positron emission tomography (PET) and morphologic changes on CT using integrated PET/CT. METHODS: We performed whole-body (18)F-fluoride PET/CT staging for 27 patients with known cancer. Tumor types comprised breast (n = 7), prostate (n = 7), and others (n = 13). A total of 154 uptake lesions were evaluated. Both tracer uptake patterns determined by (18)F-fluoride PET and morphologic patterns based on CT findings such as morphologic changes, involved locations, and grades scored using five-point scale were compared with histologic tumor subtypes and clinical laboratory data. RESULTS: CT patterns of metastatic lesion were lytic or unclassified in 26 lesions, sclerotic in 53 lesions, and mixed in 75 lesions. Multiple linear regression analysis revealed that metastatic bone lesions with high maximum standardized uptake value (SUVmax) tended to show sclerotic or mixed changes on CT (P < 0.0001), and were also distributed in bone cortex alone or both bone cortex and medulla (P < 0.0001). CONCLUSION: In patients with bone metastasis, the lesions with sclerotic or mixed changes or located in bone cortex alone or both bone cortex and medulla tend to show high SUVmax on (18)F-fluoride PET/CT.

N(1),N(12)-Diacetylspermine as a sensitive and specific novel marker for early- and late-stage colorectal and breast cancers.

PURPOSE: N(1),N(12)-diacetylspermine (DiAcSpm) in the urine of colorectal and breast cancer patients was examined to establish its usefulness as a novel diagnostic tool for detecting these cancers at clinically early stages. EXPERIMENTAL DESIGN: Urine samples from 248 colon cancer patients and 83 breast cancer patients as well as 51 patients with benign gastrointestinal diseases treated in Tokyo Metropolitan Komagome Hospital during the period of August 1999 to January 2004 were collected. DiAcSpm was analyzed by ELISA and its sensitivity for malignant conditions was compared with that of serum carcinoembryonic antigen (CEA), CA19-9, and CA15-3. RESULTS: The sensitivity of urinary DiAcSpm for colon cancer patients (n = 248) was 75.8% (mean +/- 2 SD for 52 healthy controls as a cutoff value), which was markedly higher than the sensitivities of serum CEA (39.5%, P < 0.0001) and CA19-9 (14.1%, P < 0.0001). DiAcSpm was elevated in 60% of tumor-node-metastasis cancer stage 0 + I patients, whereas only 10% (P < 0.0001) and 5% (P < 0.0001) of these patients were CEA- and CA19-9-positive, respectively. The sensitivity of urinary DiAcSpm for 83 cases of breast cancer (60.2%) was higher than the sensitivities of CEA (37.3%, P = 0.0032) and CA15-3 (37.3%, P = 0.0032). DiAcSpm was elevated in 28% of tumor-node-metastasis stage I + II patients, whereas only 3% (P = 0.0064) and 0% (P = 0.001) of these patients were CEA- and CA15-3-positive, respectively. CONCLUSION: The observations indicate that urinary DiAcSpm is a more sensitive marker than CEA, CA19-9, and CA15-3 and that it can efficiently detect colorectal and breast cancers at early stages.

[Urinary diacetylspermine: its analysis and performance as a novel tumor marker].

N1,N12-Diacetylspermine (DiAcSpm) is excreted in the urine of healthy persons as a minor component of urinary polyamine. It is a promising tumor marker, since its excretion is frequently elevated in patients with various types of cancers. DiAcSpm was first detected and characterized by HPLC fractionation followed by enzymatic detection, but more recently, antibodies highly specific for DiAcSpm was prepared, and an ELISA system applicable to determination of urinary DiAcSpm was established. Measurement of urinary DiAcSpm using this ELISA system revealed that DiAcSpm is able to detect early stage (m and sm) colon cancers which CEA and CA19-9 cannot detect. DiAcSpm may also serve as a prognostic indicator and a marker for recurrence of colon cancer. Urinary DiAcSpm is elevated in metastatic and primary brain tumors including grade 3 and 4 gliomas and primary central nervous system lymphoma. In these primary brain tumors changes in urinary DiAcSpm were well correlated with the efficacy of treatments, recurrence of disease and increased malignancy of a tumor. DiAcSpm may be useful as a comprehensive indicator of the activeness of a brain tumor lesion in a patient. DiAcSpm was elevated in hepatocellular carcinoma, but patients with liver cirrhosis also showed considerably elevated levels of DiAcSpm.