Frustration and magnetic order in alpha-CoV2O6

October 18 2012
Types d’événements
Séminaire SPCSI
Andres Saul
SPEC Bât 466 p.111 (1er ét.)
Configuration de la salle en séminaire ou réunion
30 places
Vidéo Projecteur
18/10/2012
from 11:00 to 11:00

invited by Cyrille BARRETEAU

Abstract :

CoV2O6 is currently at the center of an intense research activity due to its peculiar magnetic properties. It shows a very strong magnetocristalline anisotropy accompanied by a huge orbital contribution to its total magnetic moment (4.6 µB /Co ion instead of 3.0 µB for the spin S=3/2 only value). More interestingly, it exhibits a metamagnetic behaviour characterized by two steps in its magnetization curve for finite external fields, delimiting a plateau at 1/3 of the saturation magnetization in the absence of obvious triangular or kagome type lattice (Fig. 1(a)).

In this work, the electronic structure and magnetic properties of a-CoV2O6 are investigated using density functional theory calculations including spin-orbit coupling and orbital polarization effects.

These calculations reveal a strong magnetocristalline anisotropy with a magnetization easy axis close the c axis. Moreover, the evaluation of magnetic couplings (Fig. 1(b)) on the basis of broken-symmetry formalism suggests the occurrence of an antiferromagnetic ground-state order where ferromagnetic chains running along b are coupled antiferromagnetically to their nearest-neighbors along a and c.

Monte Carlo simulations are finally employed to explore the origins of the 1/3 plateau observed in the magnetization curves of this compound and to propose a structure for the corresponding state (Fig. 1(c)).

CINAM, Luminy