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Elastic and anelastic relaxations associated with phase transitions in EuTiO3

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Spalek, LJ 
Saxena, SS 
Panagopoulos, C 
Katsufuji, T 
Schiemer, JA 


Elastic and anelastic properties of single crystal samples of EuTiO3 have been measured between 10 and 300 K by Resonant Ultrasound Spectroscopy at frequencies in the vicinity of 1 MHz. Softening of the shear elastic constants C44 and by ~20-30% occurs with falling temperature in a narrow interval through the transition point, Tc = 284 K, for the cubic - tetragonal transition. This is accounted for by classical coupling of macroscopic spontaneous strains with the tilt order parameter, in the same manner as occurs in SrTiO3. A peak in the acoustic loss occurs a few degrees below Tc and is interpreted in terms of initially mobile ferroelastic twin walls which rapidly become pinned with further lowering of temperature. This contrasts with the properties of twin walls in SrTiO3 which remain mobile down to at least 15 K. No further anomalies were observed that might be indicative of strain coupling to any additional phase transitions above 10 K. A slight anomaly in the shear elastic constants, independent of frequency and without any associated acoustic loss, was found at ~140 K. It marks a change from elastic stiffening to softening with falling temperature and perhaps provides evidence for coupling between strain and local fluctuations of dipoles related to the incipient ferroelectric transition. An increase in acoustic loss below ~80 K is attributed to the development of dynamical magnetic clustering ahead of the known antiferromagnetic ordering transition at ~5.5 K. Detection of these elastic anomalies serves to emphasise that coupling of strain with tilting, ferroelectric and magnetic order parameters is likely to be a permeating influence in determining the structure, stability, properties and behaviour of EuTiO3.



51 Physical Sciences, 34 Chemical Sciences, 5103 Classical Physics

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Physical Review B - Condensed Matter and Materials Physics

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American Physical Society (APS)
Engineering and Physical Sciences Research Council (EP/I036079/1)
Natural Environment Research Council (NE/F017081/1)
RUS facilities were established in Cambridge through a grant from the Natural Environment Research Council of Great Britain to MAC, which is gratefully acknowledged (NE/B505738/1). LJS acknowledges the support of the National Science Centre (NCN) through Grant MAESTRO No. DEC-2012/04/A/ST3/00342. CP acknowledges Financial support in Greece through grants EURYI and MEXT-CT-2006-039047 grants, and in Singapore through Award No. NRF-CRP-4-2008-04 of the Competitive Research Programme.