Search

Epitaxial thin films of MnxGa1−x (x = 0.70, 0.74) grown on single crystal (LaAlO3)0.3(Sr2TaAlO6)0.7 [LSAT] substrates exhibit an enhanced magnetic moment and magnetic anisotropy in comparison to films of the same composition grown epitaxially on SrTiO3 [STO] single crystal substrates. Atomic and magnetic force microscopy revealed films exhibiting uniform grains and magnetic domain structures, with only minor differences between the films grown on different substrates. High resolution transmission electron microscopy on the x = 0.74 sample grown on LSAT showed a well-ordered, faceted film structure with the tetragonal c-axis oriented out of the film plane. Further, misfit dislocations, accommodating the lattice mismatch, were evidenced at the film/substrate interface. The out of plane c lattice parameter is larger for all x in the films grown on LSAT, due to the smaller substrate lattice parameter compared to STO. The increase in c generates a larger distortion of the tetragonal lattice which promotes the enhanced magnetization and magnetocrystalline anisotropy. These results indicate that LSAT is a promising substrate for realizing highly tailored magnetic properties for future spintronic applications not only in MnxGa1−x but also in the broader class of tetragonal Mn-Z-Ga (Z = transition metal) materials.

We have studied the optical and magneto-optical components of the light scattered by the surface of several Fe films with different morphologies. We present a method, based on the ratio between the optical and magneto-optical components of the scattered intensity, to discern the physical origin, either structural or magnetic corrugation, of the light scattered by these ferromagnetic surfaces. Surface versus bulk magnetic information can be separated by magneto-optical light scattering measurements, the scattered light being more sensitive to magnetization differences between surface and bulk than the reflected one., This work was performed under Spanish CICyT financial support. One of the authors (M.U.G.) thanks the Consejería de Educación y Cultura de la Comunidad de Madrid for funding. One of the authors (C.M.B.) acknowledges a grant from the Ministerio de Ciencia y Tecnología.

This letter reports the control of the c-axis orientation and the magnetic properties of L10 FePd in the well-annealed FePd/Fe thin films Fe(20 nm)/FePd(10 nm)/Fe(5 nm)/SiO2-substrate and Fe(20 nm)/FePd(5 nm)/Fe(5 nm)/SiO2-substrate, with the compositions of dual phase region in phase equilibrium. After annealing at 550 °C for 24 h, the c-axis of L1[sub 0]FePd is controlled to be oriented in the normal direction in the soft Fe matrix. These thin films exhibit the exchange-coupling of hard FePd with soft Fe, and a characteristic spring-magnet behavior showed up reversibly as a significant jump from positive to negative in the magnetization reversal.

Magnetization reversal correlation is studied as a function of the applied field angle for thin Co-films showing in-plane uniaxial magnetocrystalline anisotropy. We find that the field orientation angle has a profound effect onto the magnetization reversal process leading to a suppression of long-range correlation at sufficiently large field angles in the presence of grain alignment disorder. Correspondingly, this behavior allows for a tuning and the local confinement of magnetization reversal even in strongly exchange-coupled films and therefore presents a most desirable scenario for ultrahigh density magnetic recording.

Mn_5Ge_3C_x films with x>0.5 were experimentally shown to exhibit a strongly enhanced Curie temperature T_C compared to Mn_5Ge_3. In this letter we present the results of our first principles calculations within Green's function approach, focusing on the effect of carbon doping on the electronic and magnetic properties of the Mn_5Ge_3. The calculated exchange coupling constants revealed an enhancement of the ferromagnetic Mn-Mn interactions mediated by carbon. The essentially increased T_C in Mn_5Ge_3C is well reproduced in our Monte Carlo simulations and together with the decrease of the total magnetisation is found to be predominantly of an electronic nature.

Magnetite hollow spheres with a diameter of 650 nm and shell thickness of 40 nm exhibit an unexpected green color, in contrast with usual magnetite solids appearing black. This unusual green color is interpreted in terms of the Mie scattering on the inhomogeneous and low-density structure of the hollow spheres with a characteristic diameter that is comparable to the wavelength of the visible light. Further, thin films of the hollow spheres exhibit no two-dimensional shape anisotropy, reflecting the isotropic structure of individual particles. These results indicate the potential advantages in achieving unique physical properties through constructing hollow structures.

The authors investigated the magnetic and ferroelectric properties of hexagonally grown HoMn O3 thin films. The magnetic measurements revealed bulklike magnetic phase transitions with an additional spin-glass-like behavior feature below the N�el temperature. The ferroelectricity in the films was distinctly different from the suggested bulk behavior. Below 40 K, the HoMn O3 films showed typical ferroelectric character: their remnant polarization and coercive field values at 20 K were 3.7 ?C cm2 and 0.69 MVcm. Above 40 K, however, the films exhibited an unusual antiferroelectriclike behavior, with more pronounced features appearing at higher temperatures. These intriguing physical properties make HoMn O3 films a potential candidate material for numerous future applications. � 2007 American Institute of Physics.