Temperature evolution of the effective magnetic anisotropy in the MnCr2O4 spinel

D. TOBIA; J. MILANO; M. T. CAUSA; E. L. WINKLER

JOURNAL OF PHYSICS CONDENSED MATTER

IOP PUBLISHING LTD

Lugar: Londres; Año: 2015 vol. 27 p. 16003 - 16003

0953-8984

In this work, we present a study of the low temperature magnetic phases of polycrystallineMnCr2 O4 spinel through dc magnetization and ferromagnetic resonance spectroscopy (FMR).Through these experiments, we determined the main characteristic temperatures: TC ∼ 41 Kand TH ∼ 18 K corresponding, respectively, to the ferrimagnetic order and to the lowtemperature helicoidal transitions. The temperature evolution of the system is described by aphenomenological approach that considers the different terms that contribute to the free energydensity. Below the Curie temperature, the FMR spectra were modeled by a cubicmagnetocrystalline anisotropy to the second order, with K1 and K2 anisotropy constants thatdefine the easy magnetization axis along the direction. At lower temperatures, theformation of a helicoidal phase was considered by including uniaxial anisotropy axis along the ̄[1 1 0] propagation direction of the spiral arrange, with a Ku anisotropy constant. The valuesobtained from the fittings at 5 K are K1 = −2.3 × 104 erg cm−3 , K2 = 6.4 × 104 erg cm−3 andKu = 7.5 × 104 erg cm−3 .