Quadratic X-ray magneto-optical effect upon reflection in a near-normal-incidence configuration at the M edges of 3d-transition metals

Anisotropic magnetoresistance: materials, models and applications

Resistance of certain (conductive and otherwise isotropic) ferromagnets turns out to exhibit anisotropy with respect to the direction of magnetization: R ∥ for magnetization parallel to the electric current direction is different from R⊥ for magnetization perpendicular to the electric current direction. In this review, this century-old phenomenon is reviewed both from the perspective of materials and physical mechanisms involved. More recently, this effect has also been identified and studied in antiferromagnets. To date, sensors based on the anisotropic magnetoresistance (AMR) effect are widely used in different fields, such as the automotive industry, aerospace or in biomedical imaging.

Magneto-Optical Functions at the 3p Resonances of Fe, Co, and Ni: Ab initio Description and Experiment

We present experimental data and a complete theoretical description of the magneto-optical contributions to the complex refractive index in the extreme ultraviolet (XUV) range covering the 3p resonances of Fe, Co, and Ni. The direct comparison of the two allows us to conclude that many-body corrections to the ground state and local field effects are crucial for an accurate description of M-edge spectra. Our results are relevant for investigation of static magnetization, via XUV spectroscopy of multielement systems, as well as the dynamics of magnetization, as needed in the study of femtomagnetism and spintronics.

Nanomagnetism of Magnetoelectric Granular Thin-Film Antiferromagnets

Antiferromagnets have recently emerged as attractive platforms for spintronics applications, offering fundamentally new functionalities compared with their ferromagnetic counterparts. Whereas nanoscale thin-film materials are key to the development of future antiferromagnetic spintronic technologies, existing experimental tools tend to suffer from low resolution or expensive and complex equipment requirements. We offer a simple, high-resolution alternative by addressing the ubiquitous surface magnetization of magnetoelectric antiferromagnets in a granular thin-film sample on the nanoscale using single-spin magnetometry in combination with spin-sensitive transport experiments. Specifically, we quantitatively image the evolution of individual nanoscale antiferromagnetic domains in 200 nm thin films of Cr₂O₃ in real space and across the paramagnet-to-antiferromagnet phase transition, finding an average domain size of 230 nm, several times larger than the average grain size in the film. These experiments allow us to discern key properties of the Cr₂O₃ thin film, including the boundary magnetic moment density, the variation of critical temperature throughout the film, the mechanism of domain formation, and the strength of exchange coupling between individual grains comprising the film. Our work offers novel insights into the magnetic ordering mechanism of Cr₂O₃ and firmly establishes single-spin magnetometry as a versatile and widely applicable tool for addressing antiferromagnetic thin films on the nanoscale.

Quantitative study of the quadratic magneto-optical Kerr effects in Fe films

We present a rotating field method to separate the linear and quadratic magneto-optical Kerr effects (LMOKE and QMOKE) in Fe/GaAs(001) films. The LMOKE is isotropic in crystal orientation, while the QMOKE has both isotropic and anisotropic contributions. The experimental observation is well explained by Yeh's 4×4 matrix formalism. We also report the incident angle and the thickness dependences of the LMOKE and QMOKE, and extract the material's index of refraction n and the magneto-optical coupling constant K and G. The study gives a full description of the Kerr effect in Fe films, and the proposed method can be applied to other magneto-optical coupling systems.

X-ray magneto-optical polarization spectroscopy: an analysis from the visible region to the x-ray regime

An ultra-high vacuum compatible multipurpose chamber for magneto-optical reflection and transmission experiments with polarization analysis on magnetic systems is introduced. It is applicable in a broad photon energy range from the visible to the soft x-ray regime and for a wide angular range from grazing to normal incidence. It exploits a novel magnetization device based on rotating permanent magnets, which generates tuneable magnetic fields up to 570 mT in longitudinal, transverse and polar geometry. The unique combination of these features enables the feasibility of all typical magneto-optical spectroscopy techniques as T-MOKE, L-MOKE, P-MOKE, x-ray magneto optical linear dichroism, x-ray magnetic circular dichroism in reflection and Kerr polarization-spectroscopy, which is demonstrated for Co with focus on the Co 3p edges.