Magnetic field induced phenomena in UIrGe in fields applied along the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>b</mml:mi></mml:math> axis

Abstract

The metamagnetic transition between the antiferromagnetic and paramagnetic state in UIrGe has been studied at various temperatures by magnetization, heat capacity, and magnetocaloric-effect measurements on a single crystal in static and pulsed magnetic fields applied along the orthorhombic $b$ axis. A first-order transition is observed at temperatures below 13 K and a second-order one at higher temperatures up to the N\'eel temperature $({T}_{\mathrm{N}}=16.5\phantom{\rule{0.16em}{0ex}}\mathrm{K})$. The first-order transition is accompanied by a dramatic increase of the Sommerfeld coefficient. Magnetization measurements extended to the paramagnetic range revealed an anomalous S shape (inflection point at a magnetic field ${H}_{\mathrm{m}})$ in magnetization isotherms at temperatures above 13 K and a temperature dependence of susceptibility with a maximum at ${T}_{\mathrm{max}}$ well above ${T}_{\mathrm{N}}$. The lines representing the temperature-induced evolution of ${H}_{\mathrm{m}}$ and field-induced evolution of ${T}_{\mathrm{max}}$, respectively, are bound for the point in the magnetic phase diagram at which the order of metamagnetic transition changes. A tentative scenario explaining these anomalies by antiferromagnetic correlations or short-range order in the paramagnetic state is discussed.