Heat-Treatment-Induced Switching of Magnetic States in the Doped Polar Semiconductor Ge1−xMnxTe

Abstract

Cross-control of a material property - manipulation of a physical quantity (e.g., magnetisation) by a nonconjugate field (e.g., electrical field) – is a challenge in fundamental science and also important for technological device applications. It has been demonstrated that magnetic properties can be controlled by electrical and optical stimuli in various magnets. Here we find that heat-treatment allows the control over two competing magnetic phases in the Mn-doped polar semiconductor GeTe. The onset temperatures Tc of ferromagnetism vary at low Mn concentrations by a factor of five to six with a maximum Tc ≈ 180 K, depending on the selected phase. Analyses in terms of synchrotron x-ray diffraction and energy dispersive x-ray spectroscopy indicate a possible segregation of the Mn ions, which is responsible for the high-Tc phase. More importantly, we demonstrate that the two states can be switched back and forth repeatedly from either phase by changing the heat-treatment of a sample, thereby confirming magnetic phase-change-memory functionality.

Enhanced ferromagnetic transition temperature induced by a microscopic structural rearrangement in the diluted magnetic semiconductor Ge1−xMnxTe

“…Some of the data points plotted with small gray circles are reproduced from Ref. [49]. In the rhombohedral part of the phase diagram, the samples exhibit a huge difference in T * , depending on the heat treatment.…”

“…Some of the data points were reproduced from Ref. [49]. The dotted lines are guides to the eyes and the gray-shaded area indicates the structural-transition range.…”

“…The phase diagram in Fig. 1 is modified from the phase diagram presented in our previous publication [49]. There, the transition temperature of a sample was plotted against its magnetic moment M 7T,2K measured at T = 2 K and B = 7 T, and the corresponding Mn concentrations were labeled x m .…”

“…[49]), we investigated this system, and revealed that there are in fact two distinct magnetic phases in the low-doped region (x a 0.15; for the definition of x a see below) of the phase diagram, depending on the heat treatment of the samples. These phases are characterized by very different onset temperatures T * of magnetization (as measured in B = 0.1 T), explaining qualitatively the contradicting results found in literature.…”

“…The characteristic size of these regions was estimated to be a few tens of nm. 49 Here we present a detailed structural analysis based on highresolution synchrotron x-ray diffraction (SXRD) data. In our previous study, the complicated structural situation in the high-T * phase was only qualitatively and briefly discussed based on the roughly estimated lattice constants for one controlled-cooled sample.…”