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(Sr,Mn)TiO3 - a magnetoelectric multiglass

Subhankar Bedanta - Angewandte Physik, Universität Duisburg-Essen, Lotharstr. 1, 47048 Duisburg, Germany


Séminaire annulé

 

Multiferroic materials, in which two or more ferroically ordered states exist simultaneously, have become of great interest in recent years because of their potential applications in information storage, spintronics and sensorics. In search for these materials, systems with long range polar and magnetic order are usually considered. Here we extend this frame onto the simultaneous occurrence of two different glassy states, hence, looking for a “multiglass” scenario rather than for a multiferroic one. We study two kinds of generic disorders in Sr0.98Mn0.02TiO3 (SMnT) ceramics prepared by a mixed oxide technology [1], where the Mn2+ dopand ions are at the origin of both a polar and a spin glass with glass temperatures,
Tge  38 K and Tgm  34 K, respectively. The freezing of the polar glass triggers that of spin freezing and both glassy systems show individual memory effects. The magnetoelectric (ME) effect was measured using a modified SQUID magnetometer [2]. Even at the dilute concentration of Mn ions (2%), due to strong spin-phonon interaction within the incipient ferroelectric host crystal SrTiO3, we have observed large “paramagnetoelectric” EH2 and “magnetocapacitive” E2H2 ME coupling between both glass systems [3]. We will also discuss magnetic and dielectric data obtained on SMnT ceramics with 3% Mn, which shows, again, multiglass behavior below Tg  55 K [4].

 

References :

1. A. Tkach et al., Appl. Phys. Lett. 86, 172902 (2005).

2. P. Borisov et al., Rev. Sci. Instr. 78, 106105 (2007).

3. V. V. Shvartsman et al., Phys. Rev. Lett. 101, 165704 (2008).

4. S. Bedanta et al., (unpublished).

 

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