Abstract
Low-temperature specific heat and low-field magnetic susceptibility were measured in mixed crystals for . Three regions of composition can be distinguished in both experiments. For the crystal is paramagnetic at all temperatures. For , a spin-glass phase is observed, as evidenced by the characteristic cusp in the susceptibility and a linear temperature dependence of the specific heat in the low-temperature regions. Because the material is an insulator at low temperatures, and the Mn interactions are only antiferromagnetic, we believe that the observed spin-glass phase is produced by the frustration of the lattice. For an antiferromagnetic phase is observed. To understand the experimental behavior of the specific heat and susceptibility as a function of temperature and magnetic field for , we must assume that the distribution of Mn ions deviates strongly from a random distribution. The number of pairs is more than doubled for , and 30% higher for , than statistically predicted. The number of larger clusters, like triplets, is also significantly higher. Analysis of the data yielded the value of the exchange integral for the nearest-neighbor interaction to be K. The interaction is stronger within the larger clusters, and is described by a different exchange constant K.
- Received 25 April 1980
DOI:https://doi.org/10.1103/PhysRevB.22.3344
©1980 American Physical Society