Magnetic phase diagrams, domain switching, and quantum phase transition of the quasi-one-dimensional Ising-like antiferromagnet BaCo2V2O8

Abstract

In the effective Ising spin-1/2 antiferromagnetic chain system BaCo${}_{\text{2}}$V${}_{\text{2}}$O${}_{\text{8}}$ the magnetic-field influence is highly anisotropic. For magnetic fields along the easy axis $c$, the N\'eel order is strongly suppressed already at low fields and an incommensurate order is entered above 4 T. We present a detailed study of the magnetic phase diagrams for different magnetic field directions, which are derived from magnetization data, high-resolution thermal expansion, and magnetostriction measurements as well as from the thermal conductivity. Zero-field thermal-expansion data reveal that the magnetic transition is accompanied by an orthorhombic distortion within the $ab$ plane. Under ambient conditions the crystals are heavily twinned, but the domain orientation can be influenced either by applying uniaxial pressure or a magnetic field along the [100] direction. In addition, our data reveal a pronounced in-plane magnetic anisotropy for fields applied within the $ab$ plane. For $H\phantom{\rule{0.16em}{0ex}}\ensuremath{\parallel}\phantom{\rule{0.16em}{0ex}}[110]$, the magnetic field influence on ${T}_{\text{N}}$ is weak, whereas for magnetic fields applied along [100], ${T}_{\text{N}}$ vanishes at about 10 T and the zero-field N\'eel order is completely suppressed as is confirmed by neutron diffraction data. The second-order phase transition strongly suggests a quantum critical point being present at $H\ensuremath{\simeq}10$ T parallel [100].