Dynamic off-centering of Cr3+ ions and short-range magneto-electric clusters in CdCr2S4


The cubic spinel CdCr2S4 gained recently a vivid interest, given the relevance of relaxor-like dielectric behavior in its paramagnetic phase. By a singular combination of local probe techniques, namely, pair distribution function and perturbed angular correlation, we firmly establish that the Cr ion plays the central key role on this exotic phenomenon, namely, through a dynamic off-centering displacement of its coordination sphere. We further show that this off-centering of the magnetic Cr ion gives rise to a peculiar entanglement between the polar and magnetic degrees of freedom, stabilizing, in the paramagnetic phase, short-range magnetic clusters, clearly seen in ultralow-field susceptibility measurements. Moreover, the Landau theory is here used to demonstrate that a linear coupling between the magnetic and polar order parameters is sufficient to justify the appearance of magnetic cluster in the paramagnetic phase of this compound. These results open insights on the hotly debated magnetic and polar interaction, setting a step forward in the reinterpretation of the coupling of different physical degrees of freedom. DOI: 10.1103/PhysRevB.86.224418

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Oliveira, GNP; Pereira, AM; Lopes, AML; Amaral, JS; dos Santos, AM; Ren, Y; Mendonca, TM; Sousa, CT; Amaral, VS; Correia, JG; Araujo, JP

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The authors gratefully thank the ISOLDE Collaboration for the assistance with PAC measurements, and a special thanks to V. Tsurkan for the discussions. This work was supported by FCT-Portugal with projects PTDC/FIS/105416/2008, CERN/FP/109357/2009, and CERN/FP/116320/2010; FEDER/POCTI/n2-155/94 and the ISOLDE collaboration with approved project IS487, and the European Union: FP6 RII3-EURONS, Contract No. 506065 and FP7-through ENSAR, Contract No. 262010. Use of the Advanced Photon Source at Argonne National Laboratory was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02- 06CH11357. AMdS acknowledges the support of the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. G.N.P.O. (Grant No. SFRH/BD/80112/2011), A. M. P. (Grant No. SFRH/BPD/63150/2009), C. T. S., T. M. M., and J.S.A. (Grant No. SFRH/BPD/63942/2009) are thankful for their FCT Grants.

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