Evidence of a magnetic glass state in the magnetocaloric materialGd5Ge4

Kinetic-arrest-induced phase coexistence and metastability in(Mn,Fe)2(P,Si)

“…A similar phenomenon has been reported in diverse classes of magnetic systems, such as Gd 5 Ge 4 [16], Ni-Mn-X based Heusler alloys [17][18][19], doped-FeRh [20], Nd 7 Rh 13 [21], Tb 4 LuSi 3 [22], and manganites [23][24][25][26][27]. The kinetically arrested phase transition is associated with a strong magne-* x.f.miao@tudelft.nl tostructural coupling in these magnetic systems.…”

“…The kinetically arrested phase transition is associated with a strong magne-* x.f.miao@tudelft.nl tostructural coupling in these magnetic systems. For instance, the high-T FM to low-T AFM transition in doped-CeFe 2 alloys [13,14] is coupled with a cubic to rhombohedral structural transformation, while the high-T AFM to low-T FM transition in Gd 5 Ge 4 [16] is accompanied by the Sm 5 Ge 4 -type orthorhombic to Gd 5 Si 4 -type orthorhombic structural transition.…”

Magnetic fingerprints of the very fast jumps of colossal magnetoresistance in the phase-separated manganiteLa0.225Pr0.40Ca0.375MnMaciá1, Abril2, Hernández-Mínguez3 et al. 2008Phys. Rev. B

“…The conjunction between these spread FOPTs with a slow growing dynamic of the equilibrium low temperature phase against the metastable one gives rise to the formation of nonequilibrium "glasslike behaved" states, which are frozen below a state-dependent blocking temperature. 6 The list of known systems sharing this behavior is quickly increasing: 7,8 magnetoresistant manganites, 5,7,8 doped CeFe 2 , 9,10 magnetocaloric Gd 5 Ge 4 , 11,12 etc. The most spectacular feature displayed by these kinds of systems is perhaps the existence of fieldinduced magnetic avalanches ͑MAs͒ at low temperatures.…”

Structural and magnetic transitions inGd5SixGe4−xRyan1, Cadogan2, Cranswick3 et al. 2010Phys. Rev. BSelf Cite

“…There is a clear precedent for such a situation in this system as Gd 5 Ge 4 requires a field of order 2 T to drive the O͑II͒ → O͑I͒ structural transition below ϳ30 K. 11,20,21 Furthermore, the dynamics of the field-driven transition are complex, dominated by strong irreversibilities. 10,22 The coexistence of the O͑II͒ and O͑I͒ forms below the structural transition was clearly seen here and has been noted before 11 while hydrostatic pressures of a few gigapascal have been shown to suppress the magnetic inhomogeneities that are observed in zero-field cooled samples. 12 It is apparent from the foregoing work that the mesoscale crystal and magnetic structures of these materials below the O͑II͒ → O͑I͒ transition line are complex, exhibiting significant time, field, and temperature dependencies.…”

“…7,8 In addition, the coupled O͑II͒ → O͑I͒ / AFM→ FM transition was demonstrated to be irreversible below about 10 K, but reversible above about 20 K, 6 and an extensive phenomenology of glassy dynamics has been associated with the magnetostructural transition in Gd 5 Ge 4 . 9,10 Given that the magnetostructural transition in Gd 5 Ge 4 does not occur at all in zero field, it is not surprising that it was found to be incomplete in the Si-doped O͑II͒ materials. 11,12 Initial work suggested that FM and AFM correlations persisted in structurally uniform samples at low temperatures, 11 however a more detailed structural and x-ray magnetic circular dichroism study showed that the samples were both magnetically and structurally inhomogeneous with AFM͓O͑II͔͒/FM͓O͑I͔͒ regions coexisting below the onset of FM order.…”