Induced magnetization in La0.7Sr0.3MnO3/BiFeO3 superlattices.

Using polarized neutron reflectometry, we observe an induced magnetization of 75 ± 25 kA/m at 10 K in a La(0.7)Sr(0.3)MnO(3) (LSMO)/BiFeO(3) superlattice extending from the interface through several atomic layers of the BiFeO(3) (BFO). The induced magnetization in BFO is explained by density functional theory, where the size of band gap of BFO plays an important role. Considering a classical exchange field between the LSMO and BFO layers, we further show that magnetization is expected to extend throughout the BFO, which provides a theoretical explanation for the results of the neutron scattering experiment.

The effects of steroid hormone exposure on direct gene regulation.

Steroid hormones have been widely overlooked as controllers of gene expression. Through the mechanisms of gene expression (DNA methylation, histone methylation, and RNAi), we discuss the impact of normal reproductive templates on the pulsatility and amplitude of potential gene-regulating treatment protocols. By examining the interactions of estradiol (E2) and progesterone (P4) in women, we propose that changes in physiologic reproductive hormone templates of exposure and timing can affect fertility and even cancer through the silencing or amplification of gene products; such as P53 and Bcl-2 in women. We suggest that uncontrolled hormone levels, due to aging and/or the environment, may be restored to a normal youthful template of gene expression through the fluctuating exogenous application of E2 and P4 that mimic the normal hormonal milieu of reproductive health. Furthermore, we hypothesize that restoration of normal hormone levels may lead to a lower risk of the chronic illnesses of aging and a better quality of life in patients suffering those conditions.

Induced ferromagnetism at BiFeO3/YBa2Cu3O7 interfaces.

Transition metal oxides (TMOs) exhibit many emergent phenomena ranging from high-temperature superconductivity and giant magnetoresistance to magnetism and ferroelectricity. In addition, when TMOs are interfaced with each other, new functionalities can arise, which are absent in individual components. Here, we report results from first-principles calculations on the magnetism at the BiFeO3/YBa2Cu3O7 interfaces. By comparing the total energy for various magnetic spin configurations inside BiFeO3, we are able to show that a metallic ferromagnetism is induced near the interface. We further develop an interface exchange-coupling model and place the extracted exchange coupling interaction strengths, from the first-principles calculations, into a resultant generic phase diagram. Our conclusion of interfacial ferromagnetism is confirmed by the presence of a hysteresis loop in field-dependent magnetization data. The emergence of interfacial ferromagnetism should have implications to electronic and transport properties.

The standardization of nonsterile compounding: a study in quality control and assessment for hormone compounding.

Sterile and nonsterile compounding of medication has attracted much attention over the last few years due to the onset of various infections and negative compounding practices. This paper reports on the standardization of compounded hormones utilizing the Wiley Protocol, which provides nonsynthetic bioidentical estradiol, progesterone, dehydroepiandrosterone, and testosterone in a transdermal topical cream base for women and men in a standardized dosing regimen. Here, we present data from 2008 through 2012, which details the process of standardization and quality testing of the hormones through submission of random compounded samples for quality control and assessment. Pharmacies delivering the Wiley Protocol were required to follow the same compounding formulation, as well as submit random samples for quarterly testing. Sample concentrations were tested using high-performance liquid chromatography. We found that pharmacies that submitted samples had a 91% passing rating with a percent of target of 98.6% +/- 8.4%. It was also determined that pharmacies that prepared more compounded cream had a higher passing rating than those that prepared limited quantities. We found that standardization across multiple pharmacies could be achieved through quarterly testing of submitted samples by a third-party laboratory when following necessary procedures as defined by the Wiley Protocol. It was also determined that experience and training were a critical factor in the mixing of compounded prescriptions, with high consistency and accuracy providing patient safety.

Electron-phonon and magnetoelastic interactions in ferromagnetic Co[N(CN)2]2.

We combined Raman and infrared vibrational spectroscopies with complementary lattice dynamics calculations and magnetization measurements to reveal the dynamic aspects of charge-lattice-spin coupling in Co[N(CN)2]2. Our work uncovers electron-phonon coupling as a magnetic field-driven avoided crossing of the low-lying Co2+ electronic excitation with two ligand phonons and a magnetoelastic effect that signals a flexible local CoN6 environment. Their simultaneous presence indicates the ease with which energy is transferred over multiple length and time scales in this system.

Heisenberg pentamer: insights into inelastic neutron scattering on magnetic clusters.

Assuming Heisenberg interactions and the symmetric case of a spin S-S' pentamer, the energy eigenstates can be determined exactly. With the energies known, the inelastic neutron scattering intensities are then calculated for the special case of a 1-1/2 pentamer. Through an analysis of these results, two main insights are gained. (1) Because of symmetry constraints, not all ΔS(tot) = ±1 transitions are accessible by inelastic neutron scattering (INS). This constrains the standard selections rules for magnetic excitations. (2) The INS signatures of magnetic clusters are directly dependent on the state and component that is excited.

Spin-wave dynamics of magnetic heterostructures: application to Dy/Y multilayers.

We examine the spin-wave (SW) dynamics of Dy/Y multilayers in order to separate the contribution of the Dy-Y interface from that of bulk Dy. The SW frequencies and intensities of bulk Dy are determined analytically. When the Dy layers in a multilayer geometry are decoupled, the SW dispersion relations are discontinuous with discrete excitations. With a Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction coupling through the Y spacer, the discrete excitations become dispersive and the main SW branches split due to the multilayer geometry. Regardless of the strength of the intermediate RKKY interaction, the dispersion signature of the bulk remains.

Spin-wave instabilities and noncollinear magnetic phases of a geometrically frustrated triangular-lattice antiferromagnet.

This Letter examines the relation between the spin-wave instabilities of collinear magnetic phases and the resulting noncollinear phases for a geometrically frustrated triangular-lattice antiferromagnet in the high-spin limit. Using a combination of phenomenological and Monte Carlo techniques, we demonstrate that the instability wave vector with the strongest intensity in the collinear phase determines the wave vector of a cycloid or the dominant elastic peak of a more complex noncollinear phase. Our results are related to the observed multiferroic phase of Al-doped CuFeO2.

Spin rotation technique for non-collinear magnetic systems: application to the generalized Villain model.

This work develops a generalized technique for determining the static and dynamic properties of any non-collinear magnetic system. By rotating the spin operators into the local spin reference frame, we evaluate the zeroth, first, and second order terms in a Holstein-Primakoff expansion, and through a Green's functions approach, we determine the structure factor intensities for the spin-wave frequencies. To demonstrate this technique, we examine the spin-wave dynamics of the generalized Villain model with a varying interchain interaction. The new interchain coupling expands the overall phase diagram with the realization of two non-equivalent canted spin configurations. The rotational Holstein-Primakoff expansion provides both analytical and numerical results for the spin dynamics and intensities of these phases.

Spin-lozenge thermodynamics and magnetic excitations in Na(3)RuO(4).

We report inelastic and elastic neutron scattering, magnetic susceptibility, and heat capacity measurements for polycrystalline sodium ruthenate (Na(3)RuO(4)). Previous work suggests that this material consists of isolated tetramers of S = 3/2  Ru(5+) ions in a so-called lozenge configuration. Comparisons of magnetic susceptibility and inelastic and elastic neutron scattering results with analytic calculations for several cluster models show that although there may be significant spin-spin correlations within the lozenge cluster, a simple isolated lozenge model is not appropriate for Na(3)RuO(4).