Eur. Phys. J. B (2013) 86: 128
https://doi.org/10.1140/epjb/e2013-30672-8

Regular Article

Multiferroicity in vanadium-doped La₂Ti₂O₇: insights from first principles^*

CNR-IOM, UOS Cagliari, and Department of Physics, University of Cagliari, Cittadella Universitaria, 09042 Monserrato ( CA), Italy

^a e-mail: marco.scarrozza@gmail.com

Received: 24 July 2012
Received in final form: 18 December 2012
Published online: 4 April 2013

Abstract

We explore an unconventional route in the search for multiferroicity investigating the magnetic doping of La₂Ti₂O₇ (LTO), a ferroelectric layered perovskite, by density functional calculations. We find that substitution of Ti (in the 3d⁰ configuration) by V (3d¹) produces: (i) robust ferromagnetic (FM) order, achieving multiferroicity; (ii) structural and magnetic anisotropy, as the dopants cluster in magnetic chains. Moreover, the FM V-chains possess antiferro orbital ordering. We show that the origin of the strong FM coupling lies in the fruitful host-dopant combination: the layered structure of the host prewires the orbitals t_2g with d_xy and d_xz lower in energy, the V dopants provide the full occupancy of the bonding levels. We further address the stability of chains vs. temperature and the role of oxygen vacancies in undoped as well as Sc-doped and V-doped LTO.