Magneto-Optical Properties of Rare-Earth Terbium Ferrite-Garnet in the Near the Temperature of the Orientation Phase Transition

A model of the rearrangement of the domain structure of the Tb0.2Y2.8Fe5O12 garnet ferrite in the temperature region of the spontaneous reorientation of the easy magnetization axis is proposed, which makes it possible to consistently describe (at a qualitative level) the entire set of experimental results obtained. The latter makes it possible to make a choice in favor of the fluctuation mechanism of nucleation of domains of a new magnetic phase in the process of reorientation of the direction of the easy magnetization axis.

Magnetic Anisotropy Induced by Orbital Occupation States in La0.67Sr0.33MnO3 Film

Interface engineering is an effective and feasible method to regulate the magnetic anisotropy of films by altering interfacial states between different films. Using the technique of pulsed laser deposition, we prepared La0.67Sr0.33MnO3 (LSMO) and La0.67Sr0.33MnO3/SrCoO2.5 (LSMO/SCO) films on the (110)-oriented La0.3Sr0.7Al0.65Ta0.35O3 substrates. By covering the SCO film above the LSMO film, we transformed the easy magnetization axis of LSMO from the [001] axis to the [1\(\stackrel{\text{-}}{\text{1}}\)0] axis in the film plane. Based on statistical analyses, we found that the corresponding Mn-Mn ionic distances are different in the two types of LSMO films, causing different distortions of Mn-O octahedron in the LSMO film. In addition, it also induces diverse electronic occupation states in Mn3+ ions. The eg electron of Mn3+ occupies 3z2-r2 and x2-y2 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.

Радиальные домены в микропроводах DyPr-FeCo-B

In DyPr-FeCo-B microwires with an easy magnetization axis directed along the microwire axis, domains with radial magnetization were found by the method of magneto-optical indicator films (MOIF). The width of the radial domains decreases with increasing field up to 30 mT, and increases with increasing diameter of the microwire in the range 60 - 105 μm. In wires of smaller diameter, the critical field for the appearance of radial domains is smaller. The influence of periodic scratches on the distribution of magnetization perpendicular to the microwire is found.

Improved magnetostriction in Galfenol alloys by aligning crystal growth direction along easy magnetization axis

Galfenol (Iron-gallium) alloys have attracted significant attention as the promising magnetostrictive materials. However, the as-cast Galfenols exhibit the magnetostriction within the range of 20–60 ppm, far below the requirements of high-resolution functional devices. Here, based on the geometric crystallographic relationship, we propose to utilize the 90°-domain switching to improve the magnetostriction of Galfenols by tuning the crystal growth direction (CGD) along the easy magnetization axis (EMA). Our first-principles calculations demonstrate that Pt doping can tune the CGD of Galfenol from [110] to [100], conforming to the EMA. Then, it is experimentally verified in the (Fe0.83Ga0.17)100−xPtx (x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) alloys and the magnetostriction is greatly improved from 39 ppm (x = 0, as-cast) to 103 ppm (x = 0.8, as-cast) and 188 ppm (x = 0.8, directionally solidified), accompanying with the increasing CGD alignment along [100]. The present study provides a novel approach to design and develop high-performance magnetostrictive materials.

Возможности магнитного псевдорезонанса в изучении тонких ферромагнитных пленок с одноосной магнитной анизотропией

Possibilities of magnetic pseudoresonance (a non-resonance peak of magnetic susceptibility) were studied and compared with the ferromagnetic resonance (FMR) in measuring the parameters of thin ferromagnetic films with in-plane uniaxial magnetic anisotropy. The measurements were conducted with two characteristic samples of ferromagnetic films showing this effect. A Q -meter operating at a frequency near 300 MHz (for pseudoresonance) and a standard X -band magnetic resonance spectrometer (for FMR) were used. The Q -meter working at 300 MHz was shown to detect reliably the magnetic pseudoresonance in both epitaxial and polycrystalline films. It was found that the accuracy of determination of the magnetic anisotropy field and orientation of the easy magnetization axis provided by the pseudoresonance method is as good as with FMR, and in some cases the pseudoresonance method gives additional information.

Structural and magnetic characteristics of the Co/Cu/Co thin-film systems

The results on investigation of structural and magnetic characteristics of Co/Cu/Co thin-film systems obtained by magnetron sputtering on glass substrates are presented. The thickness of Co layers in all samples is equal to 5 nm and the Cu layer is varied from 0.5 to 4 nm. It is found that the saturation field, HS, oscillates in magnitude with increasing Cu layer thickness with the period of the order of 1 nm. The maximum values of HS are observed for tCu = 1.4, 2.2 and 3.2 nm. The hysteresis loops measured for these samples in a magnetic field applied along the easy magnetization axis have a two-step form, and for other tCu – rectangular one. The obtained results are explained by the presence of exchange coupling between the ferromagnetic layers through a Co spacer and its oscillating behavior with changing tCu.

Competing anisotropy in the (TmxPr1-x)2Fe17 system

The magnetization curves of magnetically aligned finely powdered samples of the (TmxPr1-x)2Fe17 compounds have been measured at 4 K. The easy magnetization axis is oriented in the basal plane or along the hexagonal axis for the compounds with x = 0-0.3 and 0.7-1, respectively. This is because of the absence of magnetic ordering in the Tm and Pr subsystems in these ranges, respectively, and because of competing anisotropy of the subsystems. For the compositions with x = 0.4-0.6, both rare-earth subsystems are magnetically ordered and the easy magnetization axis is oriented between the basal plane and the hexagonal axis. The critical fields of FOMPs decrease quickly as the Pr or Tm content decreases in the ranges 0-0.3 and 0.7-1, respectively. The magnetization anisotropy also diminishes as the Tm content becomes smaller than x = 0.7. No influence of the intrinsic microdeformations on the magnetization of the compounds was detected.