Magnetic phase diagram, magnetoelastic coupling, and Grüneisen scaling in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi mathvariant="normal">CoTiO</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:math>
Marco Hoffmann, K. Dey, J. Werner, Rabindranath Bag, J. Kaiser, Hubert Wadepohl, Y. Skourski, Mahmoud Abdel-Hafiez, Surjeet Singh, R. Klingeler
Abstract
High-quality single crystals of ${\mathrm{CoTiO}}_{3}$ are grown and used to elucidate in detail structural and magnetostructural effects by means of high-resolution capacitance dilatometry studies in fields up to 15 T which are complemented by specific heat and magnetization measurements. In addition, we refine the single-crystal structure of the ilmenite ($R\overline{3}$) phase. At the antiferromagnetic ordering temperature ${T}_{\mathrm{N}}$ pronounced $\ensuremath{\lambda}$-shaped anomaly in the thermal expansion coefficients signals shrinking of both the $c$ and $b$ axes, indicating strong magnetoelastic coupling with uniaxial pressure along $c$ yielding six times larger effect on ${T}_{\mathrm{N}}$ than pressure applied in-plane. The hydrostatic pressure dependency derived by means of Gr\"uneisen analysis amounts to $\ensuremath{\partial}{T}_{\mathrm{N}}/\ensuremath{\partial}p\ensuremath{\approx}2.7(4)\phantom{\rule{4pt}{0ex}}\mathrm{K}/\mathrm{GPa}$. The high-field magnetization studies in static and pulsed magnetic fields up to 60 T along with high-field thermal expansion measurements facilitate in constructing the complete anisotropic magnetic phase diagram of ${\mathrm{CoTiO}}_{3}$. While the results confirm the presence of significant magnetodielectric coupling, our data show that magnetism drives the observed structural, dielectric, and magnetic changes both in the short-range ordered regime well above ${T}_{\mathrm{N}}$ as well as in the long-range magnetically ordered phase.