Abstract
An ab initio scheme is developed and used to investigate finite-temperature properties of a prototype of the complex rare-earth iron garnets, namely, (that is, possessing gadolinium as its rare-earth ion), under applied magnetic fields. It is found that such a system undergoes a field-induced transition at a critical temperature, , at which all magnetic ions reverse the direction of their spins. This critical temperature is well seen via a peak in the specific heat versus temperature curve under field and depends on different magnetic fields’ magnitude regimes: (1) for fields up to about 20 T, it is field independent, rather sudden, and coincides with the so-called compensation temperature, K, at which the sum of all local magnetic moments is annihilated; (2) for fields larger than 70 T, there is no more full cancellation of these local magnetic moments for any temperature and is also field independent but now occurs via rotation of the local magnetic moments and at a temperature smaller than the zero-field by about 100 K; and (3) for intermediate fields ranging between 20 and 70 T, is now field dependent and decreases with the field's magnitude while also being associated with a rotation of these local magnetic moments. Our calculations also highlight the predominant role of the spins of the Gd ions in all these effects.
1 More- Received 2 June 2020
- Revised 9 September 2020
- Accepted 18 September 2020
DOI:https://doi.org/10.1103/PhysRevB.102.144406
©2020 American Physical Society