Field-induced vortex-like textures as a probe of the critical line in reentrant spin glasses
N. Martin (Université Paris-Saclay, Paris)
L. J. Bannenberg (TU Delft - RST/Storage of Electrochemical Energy, TU Delft - RID/TS/Instrumenten groep)
M. Deutsch (Lorraine University)
C. Pappas (TU Delft - RST/Neutron and Photon Methods for Materials)
G. Chaboussant (Université Paris-Saclay, Paris)
R. Cubitt (Institut Laue Langevin)
I. Mirebeau (Université Paris-Saclay, Paris)
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Abstract
We study the evolution of the low-temperature field-induced magnetic defects observed under an applied magnetic field in a series of frustrated amorphous ferromagnets (Fe1-xMnx)75P16B3Al3 (“a-Fe1-xMnx”). Combining small-angle neutron scattering and Monte Carlo simulations, we show that the morphology of these defects resemble that of quasi-bidimensional spin vortices. They are observed in the so-called “reentrant” spin-glass (RSG) phase, up to the critical concentration xC≈ 0.36 which separates the RSG and “true” spin glass (SG) within the low temperature part of the magnetic phase diagram of a-Fe1−xMnx. These textures systematically decrease in size with increasing magnetic field or decreasing the average exchange interaction, and they finally disappear in the SG sample (x= 0.41), being replaced by field-induced correlations over finite length scales. We argue that the study of these nanoscopic defects could be used to probe the critical line between the RSG and SG phases.
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