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DF: Fachverband Dielektrische Festkörper

DF 5: Multiferroics II (Joint Session of MA, DF, KR, DS)

DF 5.14: Vortrag

Montag, 22. März 2010, 17:30–17:45, H3

Magnetoelectric effect in diluted antiferromagnet PbFe_0.5Nb_0.5O₃ — •Vladimir Shvartsman¹, Pavel Borisov², Wolfgang Kleemann², and Antoni Kania³ — ¹Institut für Materialwissenschaft, Fakultät für Ingenieurwissenschaften, Universität Duisburg-Essen, Essen, Germany — ²Angewandte Physik, Fakultät für Physik, Universität Duisburg-Essen, Duisburg, Germany — ³Institute of Physics, University of Silesia, Katowice, Poland

Multiferroics, i. e. materials where two primary ferroic order parameters of magnetic and electric nature coexist, are of significant scientific and practical interest nowadays. Especially attractive are the multiferroics with enhanced magnetoelectric (ME) properties, which relate changes of polarization/magnetization to external magnetic/electric fields, respectively. While the linear ME effect has strong symmetry requirements and is rare, higher order ME couplings are allowed in all multiferroics. We report on investigations of magnetic and ME properties of (001)-oriented PbFe_0.5Nb_0.5O₃ (PFN) single crystals in the temperature range 5-300 K. PFN is ferroelectric below 385 K and antiferromagnetic below the Néel temperature, T_N=154 K. Temperature dependences of the magnetization exhibit a step like anomaly at T_N and a maximum on zero-field cooled curves at 8 K. Below T_N, the system manifests a spontaneous second order ME effect (electrobimagnetic effect), which reaches a peak value around 20 K. Moreover, after field cooling the linear ME effect has been observed, which disappears above 8 K. The nature of the low-temperature magnetic anomaly and the temperature dependences of the ME effects are discussed.