Abstract
High-resolution heat-capacity and thermal-expansion measurements on single crystals of the kagome-staircase compounds (CoNi)VO are presented. The parent compounds CoVO and NiVO undergo a sequence of first- and second-order magnetic phase transitions. The low-temperature ( K) magnetic entropy evolves monotonically with the doping content from the full value expected for Ni magnetic moments in NiVO to only half the value expected for Co moments in CoVO. The thermal-expansion coefficients (, , and ) show a strong anisotropy for all (CoNi)VO compounds. The low-temperature expansivities indicate that Co doping (Ni doping) yields changes similar to uniaxial pressures along or (). Linear Grüneisen parameters are extracted for the three main axes and are found to exhibit a complex temperature and doping dependence. For each axis, and exhibit a sign change at low temperature at the critical concentration where the incommensurate magnetic propagation vector changes. Our study motivates further investigations to understand how the multiple and complex parameters such as magnetic frustration, magnetic anisotropy, and mixture of and ions affect the rich magnetoelastic properties of (CoNi)VO.
3 More- Received 12 July 2011
DOI:https://doi.org/10.1103/PhysRevB.84.184429
©2011 American Physical Society