Low Temperature Magnetoelasticity and Internal Friction of an Amorphous Reentrant Spin Glass

Abstract
We have studied the magnetomechanical behavior of the amorphous metal METGLAS 2826A (Fe₃₂Ni₃₆Cr₁₄P₁₂B₆) in the as-quenched and annealed states at temperatures 50mK<T<10K, magnetic fields B<3T and at frequencies <3kHz. The alloy is ferromagnetic below 240K and shows a reentrant spin glass transition at T_f = 1.2K. The acoustic properties in the as-quenched and in the early stage of annealing states show strong anomalies at the spin glass transition. These anomalies vanish for a field of 0.07 T applied parallel to the main surface of the sample. Due to demagnetization effects the field dependence of magnetoelastic properties at T_f depends strongly on the angle between magnetic field and main surface of the sample. We show that the "Giant Δ E effect" observed in this sample is a consequence of the macroscopic magnetization of the sample. The sample in the amorphous and partially crystallized states shows no glasslike behavior in the acoustic properties which is usually observed in amorphous and polycrystalline metals.