International audienceRecently, nanoscale spin-crossover (SCO) particles have been the subject of great interest. The change in the 3d electronic configuration of the metal ion results in significant changes in the metal-ligand bond length and geometry, as well as in the molecular volume. Hence the spin switching process is accompanied by a remarkable change in the color, mechanical properties, dielectric properties, and magnetic susceptibility. The synthesis and investigation of these materials at reduced length scales is central not only to the exploration of fundamental effects of size reduction in these systems, but also for the development of new functional materials with applications, including guest molecule sensing, memory devices, and molecular switche
We explore the magnetic anisotropy of GaMnAs ferromagnetic semiconductor by Planar Hall Effect (PHE) measurements. Using low magnitude of applied magnetic field (i.e., when the magnitude H is smaller than both cubic Hc and uniaxial Hu anisotropy field), we have observed various shapes of applied magnetic field direction dependence of Planar Hall Resistance (PHR). In particular, in two regions of temperature. At T < Tc/2, the "square-shape" signal and at T > Tc/2 the "zigzag-shape" signal of PHR. They reflect different magnetic anisotropy and provide information about magnetization reversal process in GaMnAs ferromagnetic semiconductor. The theoretical model calculation of PHR based on the free energy density reproduces well the experimental data. We report also the temperature dependence of anisotropy constants and magnetization orientations. The transition of easy axis from biaxial to uniaxiale axes has been observed and confirmed by SQUID measurements.
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