Abstract
The magnetization and sound propagation in single-crystalline ErFe5Al7 (tetragonal crystal structure) have been studied in steady (up to 18 T) and pulsed magnetic fields (up to 60 T). The compound orders ferrimagnetically at a Curie temperature T-C=201 K and has a compensation point at T-comp=34 K.
ErFe5Al7 displays a strong magnetic easy-plane anisotropy. A strong magnetic anisotropy is present as well within the basal plane; the [100] axis is the easy magnetization direction with a spontaneous magnetic moment M-s=1.3 mu B/f.u. at 2 K.
Field-induced magnetic transitions, two along the [100] axis and two along the [110] axis, have been found in the vicinity of T=T-comp. Changes in the magnetic state at the transitions result in significant alterations of the spin-phonon coupling, which is manifested by sharp anomalies in the sound velocity and sound attenuation.
Along the easy [1001 axis the forced ferromagnetic state is reached in a field of about SOT at 2 K. whereas along the [1101 direction saturation is expected only above 60 T. A magnetic field-temperature phase diagram has been extracted up to 60 T.
From the experimental data a value of n(ErFe) = 3.3 T/mu(B) for the inter-sublattice Er-Fe exchange interaction has been obtained.