Abstract
A local electronic theory of transition-metal magnetism at finite temperatures is presented, which takes into account longitudinal and transverse spin fluctuations on the same footing. The magnetic properties are determined in the framework of a rotational-invariant -band model Hamiltonian by applying a four-field Hubbard-Stratonovich functional-integral method in the static approximation. The role of transverse spin excitations on the temperature-dependent magnetic properties is investigated by performing alloy averages in the single-site virtual crystal approximation. Bulk Fe is considered as the representative example for the applications. Results are given for the average magnetization , for the spin-excitation energies, and for the transverse and longitudinal contributions to the local magnetic moments at atom . The importance of noncollinear spin excitations is quantified by comparison with the corresponding collinear calculations. An important reduction of about 33% of the calculated Curie temperature is obtained, which now amounts to 1250 K and is thus relatively close to the experimental value. The longitudinal (transverse) components of are found to decrease (increase) as a function of temperature until the full rotational symmetry is reached at . This reflects the increasing importance of the transverse spin fluctuations. The origin of the temperature dependence of and is analyzed in terms of the local spin-fluctuation energies.
- Received 15 October 2013
- Revised 24 April 2015
DOI:https://doi.org/10.1103/PhysRevB.91.184408
©2015 American Physical Society