Vibhakar, AM; Khalyavin, DD; Manuel, P; Liu, R; Yamaura, K; Belik, AA; Johnson, RD; (2020) Effects of magnetic dilution in the ferrimagnetic columnar ordered Sm2 MnMnMn4-x Tix O12 perovskites. Physical Review B , 102 (21) 10.1103/PhysRevB.102.214428.

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Abstract

Powder neutron-diffraction experiments have been employed to establish the effects of site-selective magnetic dilution in the Sm2MnMnMn4-xTixO12 A-site columnar ordered quadruple perovskite manganites (x=1, x=2, and x=3). We show that in all three compositions the Mn ions adopt a collinear ferrimagnetic structure below 27, 62, and 34 K, respectively. An unexpected increase in the ordering temperature was observed between the x=1 and x=2 samples, which indicates a considerable departure from mean-field behavior. This result is corroborated by large reductions in the theoretical ground-state magnetic moments observed across the series, which indicate the presence of spin fluctuations and/or disorder. We show that long-range magnetic order in the x=3 sample, which occurs below the percolation threshold for B-B exchange, can only be understood to arise if it is mediated via both A-B and B-B exchange, hence confirming the importance of A-B exchange interactions in these materials. Finally, we show that site-selective magnetic dilution enables the tuning of a ferrimagnetic compensation point and the introduction of temperature-induced magnetization reversal.

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