In-plane Magnetization Components Research Articles

High-temperature photomagnetism in Co-doped yttrium iron garnet films

Magnetization processes in $(\mathrm{YCa}{)}_{3}(\mathrm{FeCoGe}{)}_{5}{\mathrm{O}}_{12}$ epitaxial films induced by linearly polarized argon laser light $(\ensuremath{\lambda}=0.488\phantom{\rule{0ex}{0ex}}\ensuremath{\mu}\mathrm{m}$) were observed at room temperature. These processes happened through a displacement of boundary between magnetic domain phases with different in-plane magnetization components. The direction and amplitude of the displacement depended on the polarization direction and light intensity. The results are explained within the scope of a phenomenological theory of photoinduced anisotropy. The microscopic origin of the photomagnetic effect in investigated materials is qualitatively discussed.

Linear and quadratic magneto-optical measurements of the spin reorientation in epitaxial Fe films on MgO

We have undertaken a detailed study by magneto-optical techniques of in-plane magnetization reversal behaviour in epitaxial Fe films grown by MBE on (10 0) oriented MgO substrate. We measure M H loops for both orthogonal in-plane magnetization components M t (component parallel to the magnetic field) and M t (component perpendicular to the field) and for various orientations of the magnetic field with respect to the crystalline axis. These measurements show the classical four-fold cubic anisotropy for large Fe film thickness and confirm the appearance of weak uniaxial in-plane anisotropy superimposed for thinner films ( t = 20 A ̊ ). We have demonstrated the appearance of strong asymmetrical hysteresis loop for p-polarized incident light. We explain this behaviour as the mixing of transverse magnetization contribution to the longitudinal magnetization measurements on the basis of quadratic magneto-optical effects. The calculation of these effects based on eigenmode propagation in anisotropic layered media are developed by including the second-order magneto-optical terms in the permittivity tensor characteristic of a cubic crystal. The second-order reflection coefficients are discussed in the case of the normal incidence of the laser beam and for the magnetic field along the hard axis of the Fe film.

Role of remanent domain structure and cubic anisotropy in the reorientation phase transition of ultrathin Ag/Fe/Ag(001) epitaxial films

We have performed a detailed ex situ magneto-optical investigation into the magnetic properties of wedged ultrathin epitaxial Ag/Fe/Ag(001) films as a function of both temperature and Fe thickness. The Fe thickness dependent reorientation phase transition (RPT) of the magnetic easy direction from out-of-plane to in-plane has been studied at various temperatures in the range 2--180 K. By using the polar Kerr effect and the Cotton-Mouton effect in reflection we were able to probe simultaneously the out-of-plane and in-plane magnetization components. We report the thermally activated formation of an out-of-plane domain structure at remanence:mat low temperatures the structure can only nucleate for small perpendicular anisotropy, i.e., close to the RPT Fe thickness; at higher temperatures nucleation is possible for Fe thicknesses well below the RPT thickness. We also report that the bulk cubic anisotropy term, ${\mathrm{K}}_{1}$, changes sign in the vicinity of the RPT Fe thickness. Consequently, we are able to delineate an Fe thickness-temperature phase diagram which identifies at least one point in (Fe thickness, temperature) space where the RPT coincides with vanishing ${\mathrm{K}}_{1}$. The identification of such a point is a necessary step towards the realization of a two-dimensional Heisenberg magnet.

Spin-reversed quasielectron excitations in the -filling fractional-quantum-Hall-effect state

We report on the effect of an in-plane magnetic field component on the magnetoresistance of the two-dimensional electron system (2DES) and capacitance between the 2DES and gate. The appearance of the \ensuremath{\nu}=1/3 and \ensuremath{\nu}=2/3 fractional-quantum-Hall-effect (FQHE) states has been observed to modify the effect at \ensuremath{\nu}\ensuremath{\gtrsim}2/3. Our results imply the existence of the spin-reversed quasielectron excitations in the \ensuremath{\nu}=2/3 FQHE. Charged excitations with large numbers of reversed spins (skyrmions) recently predicted for the \ensuremath{\nu}=1/3 FQHE state have not been found.

Growth and Properties of Multilayered Ba- and Sr-Ferrites' Films

Thin films of c-axis oriented Ba- and Sr-hexaferrits (BaM and SrM) were prepared by reactive evaporation method without any post heat treatments. Subsequently growth of BaM/SrM multilayered films was tried and the sidebands in XRD clearly appeared. According to magnetization measurements all films had the perpendicular magnetic anisotropy. However the Ms for BaM film was only 55% of that for the bulk. A broad background in Mossbauer spectrum for the BaM suggested the fluctuating magnetic moments. Though the Ms for SrM film was improved it had some inplane magnetization components. To combine the advantages of BaM and SrM individual films, the BaM/SrM multilayered film exhibited good magnetic properties: The Ms was recovered to about 80% of the bulk value and the triplane magnetization components disappeared in both the magnetization curves and the Mossbauer spectrum.

Magneto-optical measurements of magnetization reversal in nanometer scale sputtered Fe thin films

We present a magneto-optical study of the magnetic behavior of sputtered iron films of various thickness ranging from 2 to 50 nm grown on a silicon substrate. First we calculate the reflection coefficients in the case of an homogeneous magneto-optical layer with in-plane magnetization. Then we describe a technique in which both in-plane magnetization components are detected. Because of the axial deposition procedure, iron films exhibit in-plane uniaxial anisotropy depending on the thickness of the layer. In particular, we show that, for 4 nm thickness, anisotropy induced by slightly tilted columnar growth can be observed, whereas for larger thicknesses this in-plane anisotropy vanishes. Using an accurate acquisition system based upon a rapid analog-to-digital converter we measured the rapid magnetization reversal. The field sweep rate was varied between 100 Oe/s and l MOe/s. We interpret the observed dynamical effects in terms of wall movement and microdomain reversal.

Magnetic reconstruction of the Gd(0001) surface.

The surface magnetism of Gd(0001) films is studied using spin resolved electron spectroscopies. Both a canted surface magnetization vector out of the plane of the film and an enhanced surface magnetic ordering temperature 60[plus minus]2 K higher than the bulk Curie temperature are observed. Our results show that the surface magnetic layer behaves as a separate entity from the bulk. The in-plane component of surface magnetization aligns ferromagnetically to the bulk. Spin resolved photoemission from the Gd 4[ital f] core levels shows [approx]65% spin polarization at 150 K, which extrapolates to [approx]91% at 0 K.

Magnetization reversal in (100) Fe thin films.

The longitudinal and transverse magneto-optical Kerr effects have been used for understanding the magnetization processes in single crystal Fe/GaAs (100) thin films. By using both of these Kerr effects it is possible to concurrently detect two orthgonal in-plane magnetization components. Presented here are Kerr hysteresis curves for magnetic fields directed along the in-plane 〈100〉 and 〈110〉 directions of the Fe films. For the 〈100〉 direction the magnetization curves are square, while for the 〈110〉 unusual overshoots are present in the Kerr hysteresis curves. In order to understand the origin of these curves for the 〈110〉 direction, simulations were done using the Fresnel reflection coefficients for the in-plane Kerr effects and a coherent-rotation model for the magnetization process. There is good agreement between the simulated Kerr hysteresis curves and the experimental data. The overshoots along with the general analyzer dependence of the hysteresis curves are reproduced in the simulations. However, the magnitude of the reversal and saturation fields of the modeled loops cannot be brought into agreement with the data. For applied fields near the 〈110〉 directions, the analysis suggests that the reversal occurs through the nucleation and/or unpinning of 90\ifmmode^\circ\else\textdegree\fi{} domains at two distinct transition fields followed by coherent rotation.

Detecting two magnetization components by the magneto-optical Kerr effect

A novel technique was detecting two orthogonal in-plane magnetization components is presented. This technique utilizes the magneto-optical Kerr effects to sense the two components. These components of magnetization are parallel and perpendicular to the plane of incidence of the light beam. The ability to sense two components, individually or simultaneously, is a result of the disparity in the longitudinal and transverse Kerr effects. Based on the Frensel reflection coefficients of these two effects, an anlysis is presented describing this dual component sensitivity. The physical conditions are given for simultaneous and individual detection of the two in-plane magnetization components. To substantiate this analysis, magneto-optical measurements are made on single-crystal Fe films. The results are discussed in the context of dual component sensitivity.

Magnetic microstructure of the (0001) surface of hcp cobalt

The magnetic domain structure of the (0001) surface of a hcp cobalt crystal was investigated using scanning electron microscopy with polarization analysis (SEMPA). This is the first observation by SEMPA of both out-of-plane and in-plane magnetization components. The perpendicular magnetization imaged with SEMPA showed a branched structure very similar to that previously observed by magneto-optic Kerr microscopy. In addition, a previously unobserved in-plane magnetic substructure was measured. The in-plane magnetization is divided into well-defined submicron domains that appear to reflect the sixfold symmetry of the crystal surface.

ポーラ・カー磁化曲線測定装置における磁場垂直度の精密測定法

The polar Kerr magnetooptical effect has been used as the main method to measure the magnetization characteristics of films with perpendicular magnetic anisotropy. The author found, however, that on some occasions the shape of the polar Kerr loop as well as the Hall loop changed remarkably (or drastically in some cases) with the orientation of the sample in the investigation of rare earth-transition metal alloy amorphous films. This is due to the cooperative effect of the in-plane or oblique component of magnetization in the sample film and the imperfect perpendicularity of the magnetic field in the polar Kerr apparatus. There is a possibility that such an effect leads to serious errors and misunderstanding in the measurement of perpendicular anisotropy films containing in-plane magnetic component, because some degree of deviation of field from the film normal is unavoidable in actual polar Kerr systems. Therefore, it is very important to examine the perpendicularity of the magnetic field of the magnet in the polar Kerr system before the experiment. However, it is difficult to measure the deviation angle of magnetic field by the ordinary techniques. This paper presents an original method to measure the perpendicularity of the magnetic field using an evaporated nickel thin film with oblique uniaxial magnetic anisotropy. In this method, the deviation angle of field can be obtained from the ratio of the maximum coercivity to the minimum one of the Hall or Kerr loop when the Ni film is rotated on the sample stage.

Distribution of magnetization in elements on chevron detector

The magnetization distribution in elements of bubble domain chevron detector is first investigated using the magnetooptical micromagnetometer technique. Distribution curves of in-plane magnetization components are obtained in all types of elements. It is found that the magnetization distribution in elements having interconnections is very different from those having none. It is shown that the magnetization distribution in a chevron which is in row, is not equivalent to the one beyond it. It is shown that the magnetization component on the chevron leg perpendicular to the field is more than zero and amounts to M s at the center of the chevron. Fields are determined in which there are remagnetization and redistribution of magnetization in bubble domain chevron detector.

Pulse superposition and high-density recording

The variation of output voltage with packing density in high-density digital tape recording has been shown to be consistent with the occurrence of a form of pulse superposition. Conditions necessaxy for this to be the superposition of isolated pulse shapes have been produced first using a model of the magnetization distribution in the tape which involves only in-plane components of magnetization and secondly using a model with a 'vector' magnetization distribution. The weakness of the theory is that it predicts symmetrical pulse shapes whereas those observed in practice are asymmetrical. Nevertheless, most of the experimental results satisfy the first derived condition, although some of the results need the assumption of certain types vector distribution, as a minimum, if they are to be explained. It is concluded, in the absence of knowledge of the real distributions, that while superposition is occurring it may not always be the superposition of isolated pulse shapes.

Structure and Origin of New Stripe Domains in Oblique-Incidence Permalloy and Ni Films

Stripe domains were observed in oblique-incidence 40-100% Ni-Fe films prepared at incident angles from 57° to 75° with thicknesses above 450A of either sign of uniaxial anisotropy. Lorentz microscopy at 100 kV reveals the structure of the domains as follows: 1. domain width is 1000-3500A and constant within a film, 2. in-plane component of magnetization is parallel to the incident direction, thus they are named “negative stripe domain”, 3. magnetization inclines at an angle below 60° from the film plane, and 4. both normal and in-plane components of magnetization change the direction in two neighboring domains. This structure can be considered analogous to that of an expanded cross-tie wall. At low frequency magnetization reversal, the negative stripe domains behave as a group and cause a two-stepped constricted hysteresis loop. The origin of these negative stripe domains is discussed in connection with the shape and pile of elongated columnar grains.