Spin glassiness and ferromagnetism in disordered Ni-Mn (invited)

Abstract

With decreasing Mn concentration near 25 at. %, disordered Ni-Mn alloys are seen to evolve from a characteristic spin-glass behavior, with the magnetic polarizability rapidly increasing, to a magnetic behavior that signifies the onset of ferromagnetic order and the appearance of a spin-glass-like phase at lower temperatures. Moreover, the latter phase is ‘‘mixed’’ in that its equilibrium state (in the fields applied during cooling) manifests a spontaneous ferromagnetic moment, while its magnetization reversals with field exhibit the unidirectional anisotropy of a spin glass. The unusual magnetic properties of the mixed phase in the zero-field-cooled state can be ascribed to a domain structure in which the domains have unidirectional anisotropies of random orientation.

Pressure effect on magnetic moments in ordered Ni3Mn and disordered Ni100−xMnxalloys:ab initiocalculation and experiment

“…The presence of the Cu 3 Au-type superstructure was confirmed in the NiMn alloys with compositions close to this critical content of Mn [1,4]. A mix of ferromagnetic and spin glass behavior was described in the disordered NiMn alloys with the almost critical Mn content at temperatures below 100 K [3] …”

“…The local moment in the Ni sites is very sensitive to the total moment of the alloys. It can be seen from the extraordinarily low value of m(Ni) in the disordered Ni 75 Mn 25 alloy that is on the verge of an existence of the magnetic state in the NiMn disordered alloys[1][2][3][4]8,9]. However, regardless of the behavior of m(Ni), the significant changes of m(Mn±) under pressure can be considered as the dominant effect in the extraordinary pressure behavior of magnetization of the disordered NiMn alloys.…”

“…The strong dependence of magnetic properties of NiMn alloys on their chemical composition and structural ordering has been studied intensively for many years [1][2][3][4][5][6][7]. The Mn-rich Ni 1−x Mn x solid solutions crystallize in the face-centered cubic (fcc) structure.…”

Spin-glass-like behavior of CaNi1−xMnxGe

“…The results of the present work clearly demonstrate that the magnetic behavior of the CaNi 1-x Mn x Ge is characterized by the coexistence of magnetic glassy state and FM ordering, which is quite similar to the systems of Ni-Mn, in which FM and SG coexist. 33,34 Such magnetic behavior has not been reported for 111-and 122-type compounds containing MnX 4 (X = Si, Ge) tetrahedrons diluted with "nonmagnetic" T mX 4 units. However, similar glassy ferromagnetism has been found in many ordered and disordered magnetic materials spanning from insulating oxides to metallic compounds, and the origin of such behavior has been always been traced to the presence of FM clusters due to compositional fluctuation or phase separation.…”

Spin textures induced by quenched disorder in a reentrant spin glass: Vortices versus “frustrated” skyrmions

“…Metallic ferromagnetic alloys with competing nearest-neighbor interactions tuned by the concentration x show a magnetic phase diagram (T, x) in qualitative agreement with mean-field predictions. Well-known examples are Ni 1−x Mn x [9], Au 1−x Fe x [10], Fe 1−x Al x [11,12], and Fe 1−x Cr x [13] crystalline alloys or amorphous Fe-based alloys [14][15][16][17][18]. A large body of experimental and theoretical studies have revealed the peculiarities of their magnetic behavior.…”