Sound-velocity anomalies in cobalt and manganese aluminosilicate glasses

Anomalous spectral density and two-level system-phonon coupling in an insulating magnetic glass

“…For the non-magnetic glasses the maximum of the sound velocity occurs at about 2 K while for the magnetic ones no maximum was observed in the explored temperature range. Analogous results in amorphous aluminosilicate spin glasses were obtained by Moran et al [16] and were explained as a negative contribution in the vicinity of the freezing temperature of the spins. All these results look similar to those we have obtained in our Mn glass.…”

“…This allows us to interpret our results in terms of amorphous properties alone and we see no evidence of magnetic effects at Tf. In particular the low temperature of the maximum and the upward curvature mentioned above are explained by the large value of the constant K3 and not by some additional magnetic effect We believe that the results of Lin and Thomas [15] and Moran et al [16] may be interpreted in the same manner. The case of metallic spin glasses (such as Cu-Mn) [17,18] is outside the scope of this discussion because of their crystalline structure, but results similar to Moran et ale are reported, i.e., a decrease in the velocity near the spin-glass temperature Tf.…”