Quantum versus classical nature of a low-temperature magnetic phase transition in TbAl${}_3$(BO${}_3$)${}_4$

Abstract

Specific heat, $C_B$, of a TbAl${}_3$(BO${}_3$)${}_4$ crystal was studied for 50 mK $<T<$ 300 K, with emphasis on $T<1$ K, where a phase transition was found at $T_c=0.68$ K. Nuclear, non-phonon ($C_m$), and lattice contributions to $C_B$ were separated. Lowering of $T_c$ with ncrease of magnetic field parallel to the easy magnetization axis, $B_{||}$, was found. It was established that $C_m$ and a Grüneisen ratio depend on $B_{||}$ and $T$ in a way characteristic of systems, in which a classical transition is driven by quantum fluctuations, QF, to a quantum critical point at $T=0$, by tuning a control parameter ($B_{||}$). The $B_{||}-T$ phase diagram was constructed and the dynamical critical exponent $0.82\le z\le 0.96$ was assessed. Nature of the transition was not established explicitly. Magnetization studies point at the ferromagnetic ordering of Tb${}^{3+}$ magnetic moments, however, lowering of $T_c$ with increase in $B_{||}$ is opposite to the classical behavior. Hence, a dominant role of QF was supposed.

arXiv commentPreprint submitted to Phys. Rev B. The final version was published (DOI: 10.1103/PhysRevB.105.094418)

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Cited by in corpus (2)

• Specific heat studies of the phase transitions in multiferroic Sr${}_{1-x}$Ba${}_x$Mn${}_{1-y}$Ti${}_y$O${}_3$ system ($0\le x\le 0.65,0\le y\le 0.1$)
• Hyperfine coupling in singlet ground state magnets