We report on the electronic properties of a U Ni13 Ru23 Al single crystal as a function of temperature and magnetic field. Our specific-heat, magnetization, and resistivity data provide strong evidence that the uranium 5f moments order ferromagnetically below TC =74 K. Magnetic measurements reveal that the c axis is the easy magnetization direction with a saturation moment of about 0.78 μB U -atom. Our neutron diffraction studies on U Ni13 Ru23 Al provide strong evidence that Ni occupies the 1b (and Ru the 2c) positions of the ZrNiAl structure. We argue that such preferential occupation of Ni and Ru atoms is responsible for the observed ferromagnetic ground state.
Bibliographical noteFunding Information:
This work was supported by the National Science Foundation (grant number DMR-0094241) and the Grant agency of The Czech Republic (grant number GACR 202/02/0739). Work at the Pulse Field Facility, NHMFL, was performed under the auspices of the NSF, the US Department of Energy, and the State of Florida.