Heat Capacity and Magnetic Phase Diagram of the Low-Dimensional Antiferromagnet Y$_2$BaCuO$_5$

TL;DR

This study investigates the magnetic phase diagram of Y$_2$BaCuO$_5$ using specific heat measurements under magnetic fields, revealing a field-dependent Neel temperature and a crossing point in specific heat curves, with comparisons to similar low-dimensional systems.

Contribution

The paper provides the first detailed phase diagram of Y$_2$BaCuO$_5$ under magnetic fields and proposes an effective field-induced magnetic anisotropy as the underlying mechanism.

Findings

Neel temperature is constant below 2 T and increases linearly above 2 T.

Identification of an isosbestic point at 20 K where specific heat curves cross.

Comparison with similar quasi-two-dimensional systems suggests common magnetic behavior.

Abstract

A study by specific heat of a polycrystalline sample of the low-dimensional magnetic system Y$_2$BaCuO$_5$ is presented. Magnetic fields up to 14 T are applied and permit to extract the ($T$,$H$) phase diagram. Below $\mu_0H^*\simeq2$ T, the N\'eel temperature, associated with a three-dimensional antiferromagnetic long-range ordering, is constant and equals $T_N=15.6$ K. Above $H^*$, $T_N$ increases linearly with $H$ and a field-induced increase of the entropy at $T_N$ is related to the presence of an isosbestic point at $T_X\simeq20$ K, where all the specific heat curves cross. A comparison is made between Y$_2$BaCuO$_5$ and the quasi-two-dimensional magnetic systems BaNi$_{2}$V$_{2}$O$_{8}$, Sr$_2$CuO$_2$Cl$_2$, and Pr$_2$CuO$_4$, for which very similar phase diagrams have been reported. An effective field-induced magnetic anisotropy is proposed to explain these phase diagrams.