Quantum relaxation in the low-temperature magnetic susceptibility of the amorphous alloya−Tb2Fe

Abstract

The ac magnetic susceptibility of melt spun ribbons of the strong-random magnetic-anisotropy amorphous alloy a-Tb 2 Fe has been measured from room temperature down to 0.10 K. In the temperature region 4ϽT Ͻ300 K the system behaves as a random anisotropy sperimagnet, with freezing temperature T f ϭ160 K. In-phase Ј and out-of-phase Љ components of the susceptibility deviate from the classical linear temperature dependence to a temperature-independent value below a crossover temperature T Q Ϸ3 K. The low-temperature ''plateau'' behavior supports the existence of magnetic quantum tunneling relaxation. The tunneling entities are spin drops which comprise an average number nϷ11 spins.

Thermal relaxation of magnetic clusters in amorphous Hf57Fe43alloy

“…The extrapolation of S(T ) to zero temperature gives the non-zero relaxation rate. It is still questionable whether such signs of quantum tunnelling of magnetization can be observed in this kind of material at lower temperatures, as has been seen in some random anisotropy magnets [39,47] and ensembles of magnetic nanoparticles [48]. Theoretical predictions say that magnetization tunnelling could be observable below ≈0.1 K [48] in our case.…”

Low-temperature heat capacity of a dipole spin glass

“…We now consider that the total heat capacity involves the phonon and magnon contributions together with the contribution of the internal degrees of freedom (the tunneling contribution [24]). Then the corresponding expression for the heat capacity assumes the following form:…”