https://doi.org/10.1140/epjb/e2015-60113-7
Regular Article
Thermodynamics of the frustrated J1-J2 Heisenberg ferromagnet on the body-centered cubic lattice with arbitrary spin
1 Institut für Theoretische Physik,
Universität Magdeburg, 39016
Magdeburg,
Germany
2 Institut für Theoretische Physik,
Universität Leipzig, 04109
Leipzig,
Germany
a
e-mail: johannes.richter@physik.uni-magdeburg.de
Received:
13
February
2015
Received in final form:
7
May
2015
Published online:
17
June
2015
We use the spin-rotation-invariant Green’s function method as well as the
high-temperature expansion to discuss the thermodynamic properties of the frustrated
spin-SJ1-J2 Heisenberg
magnet on the body-centered cubic lattice. We consider ferromagnetic nearest-neighbor
bonds J1<
0 and antiferromagnetic next-nearest-neighbor bonds J2 ≥ 0 and
arbitrary spin S. We find that the transition point between the ferromagnetic ground state and the
antiferromagnetic one is nearly independent of the spin S, i.e., it is very close
to the classical transition point
. At finite temperatures we focus on the parameter
regime
with a ferromagnetic ground-state. We calculate the
Curie temperature TC(S,J2)
and derive an empirical formula describing the influence of the frustration parameter
J2 and spin S on TC. We find that the
Curie temperature monotonically decreases with increasing frustration J2, where very
close to
the TC(J2)-curve
exhibits a fast decay which is well described by a logarithmic term
. To characterize the magnetic ordering below and above
TC, we calculate the
spin-spin correlation functions ⟨
S0SR
⟩, the spontaneous magnetization, the uniform static susceptibility
χ0 as well as the correlation length
ξ.
Moreover, we discuss the specific heat CV and the temperature
dependence of the excitation spectrum. As approaching the transition point
some unusual features were found, such as negative
spin-spin correlations at temperatures above TC even though the
ground state is ferromagnetic or an increase of the spin stiffness with growing
temperature.
Key words: Solid State and Materials
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2015