Magnetism in a UNi2/3Rh1/3Al single crystal

• Published in: Philosophical magazine (Abingdon, England) England), 2003-05, Vol.83 (13), p.1613-1633
• Main Authors: Andreev, A. V., SechovskÝ, V., ProkeŠ, K., Homma, Y., Syshchenko, O., Šebek, J., Bartashevich, M. I., Goto, T., Shiokawa, Y., Jurek, K.
• Format: Article
• Language: English
• ISSN: 1478-6435; 1478-6443
• DOI: 10.1080/1478643031000094730

We report a magnetization, magnetostriction, electrical resistivity, specific heat and neutron scattering study of a UNi 2/3 Rh 1/3 Al single crystal, a solid solution of an antiferromagnet UNiAl and a ferromagnet URhAl. The huge uniaxial magnetic anisotropy confining the principal magnetic response to the c axis in the parent compounds persists also for the solid solution. The magnetization curve at 1.6 K has a pronounced S shape with an inflection at 12 T. The temperature dependence of magnetic susceptibility exhibits a maximum around 10 K and is magnetic history dependent at lower temperatures where the resistivity increases linearly with decreasing temperature. The low-temperature ρ(T) anomaly is removed in a magnetic field applied along c, which yields a large negative magnetoresistance amounting to m46 zin 14T (at 2 K). The C/T values exhibit a minimum around 12 K and below 8 K they become nearly constant (about 250 mJ mol −1 K − 2), which is strongly affected by magnetic fields. Neutron scattering data confirm a non-magnetic ground state of UNi 2/3 Rh 1/3 Al. The bulk properties at low temperatures are tentatively attributed to the freezing of U magnetic moments with antiferromagnetic correlations. The additional intensities detected on top of nuclear reflections in neutron diffraction in a magnetic field applied along c are found to be proportional to the field-induced magnetization, which reflects field-induced ferromagnetic coupling of U magnetic moments. This scenario is corroborated also by finding low-temperature magnetostriction data that also scale with the square of magnetization.