Heat-Treatment Induced Magnetic Anisotropy of GaMnSb Films

Conditions and mechanisms of controlled variation of the magnetic anisotropy of GaMnSb films containing magnetic MnSb nanoinclusions by means of heat treatment have been determined. For this purpose, the temperature and magnetic-field dependences of the magnetic moments of samples before and after thermal annealing were measured using a SQUID magnetometer. It is established that the heat treatment of GaMnSb films leads to a significant increase in the values of characteristics determined by the magnetic anisotropy, including the growth of blocking temperature (from 95 to 390 K) and the magnetic anisotropy field (from 330 to 630 Oe). Results of transmission electron microscopy investigation indicate that a change in the magnetic anisotropy of GaMnSb films as a result of their thermal annealing can be related to a transition of the crystalline structure of magnetic MnSb nanoinclusions from hexagonal (space group P6₂/mmc) to cubic (space group F-43m).     

Band Structures of Ultrathin Bi(110) Films on Black Phosphorus Substrates Using Angle-Resolved Photoemission Spectroscopy

The band structures of two-monolayer Bi(110) films on black phosphorus substrates are studied using angleresolved photoemission spectroscopy. Within the band gap of bulk black phosphorus, the electronic states near the Fermi level are dominated by the Bi(110) film. The band dispersions revealed by our data suggest that the orientation of the Bi(110) film is aligned with the black phosphorus substrate. The electronic structures of the Bi(110) film strongly deviate from the band calculations of the free-standing Bi(110) film, suggesting that the substrate can significantly affect the electronic states in the Bi(110) film. Our data show that there are no non-trivial electronic states in Bi(110) films grown on black phosphorus substrates.     

Visualization of Dynamic Vortex Structures in Magnetic Films with Uniaxial Anisotropy (Micromagnetic Simulation)

Three-dimensional computer simulation of dynamic processes in a moving domain boundary separating domains in a soft magnetic uniaxial film with planar anisotropy is performed by numerical solution of Landau-Lifshitz-Gilbert equations. The developed visualization methods are used to establish the connection between the motion of surface vortices and antivortices, singular (Bloch) points, and core lines of intrafilm vortex structures. A relation between the character of magnetization dynamics and the film thickness is found. The analytical models of spatial vortex structures for imitation of topological properties of the structures observed in micromagnetic simulation are constructed.     

Magnetic Anisotropy Induced by Orbital Occupation States in La_(0.67)Sr_(0.33)MnO_3 Films

Interface engineering is an effective and feasible method to regulate the magnetic anisotropy of films by altering interfacial states between films.Using the technique of pulsed laser deposition,we prepared La_(0.67)Sr_(0.33)MnO_3(LSMO) and La_(0.67)Sr_(0.33)MnO_3/SrCoO_(2.5)(LSMO/SCO) films on(110)-oriented La_(0.3)Sr_(0.7)Al_(0.65)Ta_(0.35)O_3 substrates.By covering the SCO film above the LSMO film,we transformed the easy magnetization axis of LSMO from the [001] axis to the [110] axis in the film plane.Based on statistical analyses,we find that the corresponding Mn-Mn ionic distances are different in the two types of LSMO films,causing different distortions of Mn-O octahedron in LSMO.In addition,it also induces diverse electronic occupation states in Mn~(3+) ions.The eg electron of Mn~(3+)occupies 3 z~2-r~2 and x~2-y~2 orbitals in the LSMO and LSMO/SCO,respectively.We conclude that the electronic spin reorientation leads to the transformation of the easy magnetization axis in the LSMO films.     

Preparation of Fe/Pt Films with Perpendicular Magnetic Anisotropy

We have investigated the microstructures and magnetic properties of L1₀ ordered equi-atomic FePt thin films prepared by ion beam sputtering and subsequent annealing. It is observed from X-ray reflectivity and X-ray diffraction measurements that the mixing at Fe/Pt interfaces starts to occur with annealing and leading to the FePt alloy phase formation. The rapid increase in the coercivity values above 275°C, obtained from vibrating sample magnetometer (VSM) measurements, confirms the formation of the ordered L1₀ FCT FePt phase.     

Capabilities of Magnetic Pseudoresonance in Studies of Thin Ferromagnetic Films with Uniaxial Magnetic Anisotropy

Technical Physics - Possibilities of magnetic pseudoresonance (a non-resonance peak of magnetic susceptibility) were studied and compared with the ferromagnetic resonance (FMR) in measuring the...     

Theoretical studies of surface diffusion: Self-diffusion in the bcc (110) system

Self-diffusion in the bcc (110) system is studied using numerical molecular dynamics simulations. Calculations based on Lennard-Jones pair potentials extracted from fits to bulk thermodynamic data produce self-diffusion constants in excellent agreement with available experimental data.     

A Geometric Interpretation of the Effective Uniaxial Anisotropy Field in Magnetic Films

It is shown that the effective uniaxial anisotropy field that is usually applied in thin magnetic films (TMFs), which is noncollinear to the magnetization vector, is insufficient for deeper understanding of these processes, although it explains many physical processes in films. The analysis of the magnetization discontinuity in films under certain conditions yields the component of the effective uniaxial anisotropy field collinear to the magnetization vector. This component explains the magnetization discontinuity and allows one to speak of the total effective uniaxial anisotropy field in TMFs.