Effect of hydrostatic and uniaxial pressure on structural and magnetic transitions in TbNiAl

Abstract

We have studied development of structural and magnetic properties of TbNiAl single crystal under applied hydrostatic and uniaxial pressure. TbNiAl crystallizes in the hexagonal ZrNiAl-type structure. The lattice parameters show a transition between two phases with different c/a ratio around 120 K as evidenced by X-ray diffraction, resistivity and thermal expansion measurements. The application of hydrostatic pressure stabilizes the low c/a phase. The transition shifts consequently to lower temperatures with applied pressure and vanishes for pressure above 0.55 GPa. The magnetic properties are characterized by antiferromagnetic order below TN = 45 K. The application of magnetic field of 0.3 T along the c-axis leads to a metamagnetic transition to ferromagnetic order. The critical field of this transition shifts considerably to higher values with hydrostatic pressure whereas the uniaxial pressure applied along the c axis moves the transition to lower fields. TbNiAl represents thus a rare example of a well localized system where the magnetic ground state is strongly influenced by external pressure. This behavior is discussed in connection with the structural parameters.