Charge disproportionation and nano phase separation in $R$SrNiO$_4$

H. Guo; Z. W. Li; C. F. Chang; Z. Hu; C. -Y. Kuo; T. G. Perring; W. Schmidt; A. Piovano; K. Schmalzl; H. C. Walker; H. J. Lin; C. T. Chen; S. Blanco-Canosa; J. Schlappa; C. Schüßler-Langeheine; P. Hansmann; D. I. Khomskii; L. H. Tjeng; A. C. Komarek

arXiv · 2007.03544

Charge disproportionation and nano phase separation in $R$SrNiO$_4$

H. Guo·Z. W. Li·C. F. Chang·Z. Hu·C. -Y. Kuo·T. G. Perring·W. Schmidt·A. Piovano·K. Schmalzl·H. C. Walker·H. J. Lin·C. T. Chen·S. Blanco-Canosa·J. Schlappa·C. Schüßler-Langeheine·P. Hansmann·D. I. Khomskii·L. H. Tjeng·A. C. Komarek

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Abstract

We have successfully grown centimeter-sized layered $R$SrNiO$_4$ single crystals under high oxygen pressures of 120 bar by the floating zone technique. This enabled us to perform neutron scattering experiments where we observe close to quarter-integer magnetic peaks below $\sim$77 K that are accompanied by steep upwards dispersing spin excitations. Within the high-frequency Ni-O bond stretching phonon dispersion, a softening at the propagation vector for a checkerboard modulation can be observed. Together with our spin wave simulations these observations reveal that this Ni$^{3+}$ system exhibits charge disproportionation with charges segregating into a checkerboard pattern within a nano phase separation scenario rather than showing a Jahn-Teller effect.

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H. Guo, Z. W. Li, C. F. Chang, Z. Hu, C. -Y. Kuo, T. G. Perring, W. Schmidt, A. Piovano, K. Schmalzl, H. C. Walker, H. J. Lin, C. T. Chen, S. Blanco-Canosa, J. Schlappa, C. Schüßler-Langeheine, P. Hansmann, D. I. Khomskii, L. H. Tjeng, A. C. Komarek. 2020-07-07. Charge disproportionation and nano phase separation in $R$SrNiO$_4$. https://arxiv.org/abs/2007.03544

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