Regensburg 2013 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 2: Multiferroics 1 (jointly with DF, DS, KR, and MA)
TT 2.9: Talk
Monday, March 11, 2013, 11:30–11:45, H3
Tuning the multiferroic phase of CuO with impurities — •Johan Hellsvik1, Marcello Balestieri1, Alessandro Stroppa2, Anders Bergman3, Lars Bergqvist4, Olle Eriksson3, Silvia Picozzi2, and José Lorenzana1 — 1ISC-CNR, Rome, Italy — 2CNR-SPIN, L'Aquila, Italy — 3Uppsala University, Uppsala, Sweden — 4KTH, Stockholm, Sweden
The discovery that CuO is a multiferroic with a high antiferromagnetic transition temperature of 230 K opened a possible route to room-temperature multiferroicity with a strong magnetoelectric coupling [1]. CuO belongs [2] to a new class of multiferroic materials where the so called 'order by disorder mechanism' [3] plays a crucial role. In this work we study the effect of different impurities on the phase diagram of CuO aiming at engineering the multiferroic properties. Extensive density functional theory (DFT) calculations were performed for a large number of fixed spin configurations in pure CuO and CuO doped with a small fraction of the Cu atoms substituted with the nonmagnetic elements Mg, Zn or Cd, or the magnetic elements Ni or Co. Our computations established that the energy difference between the low-temperature collinear AF1 phase and the intermediate temperature multiferroic AF2 phase decreased monotonously with increasing doping level confirming that impurities favour the multiferroic phase. The magnetic phase diagram has been mapped out in Monte Carlo simulations for classical Heisenberg spins. [1] T. Kimura et al., Nature Mat. 7, 291 (2008); [2] G. Giovannetti et al., Phys. Rev. Lett. 106, 026401 (2011); [3] C. L. Henley, Phys. Rev. Lett. 62, 2056 (1989)