Structure and magnetic properties of RAlSi (R=light rare earth)

We prepared the semimetals RAlSi (R,=,light rare earth), and systematically study their crystal structures and magnetic properties. X-ray diffractions confirm the coexistence of the site-disordered phase with group space of I4_1/amd and the noncentrosymmetrically ordered phase with space group of I4_1md in RAlSi alloy. The ordered phase is the main phase in RAlSi alloy. RAlSi alloys show nonmagnetic character for \rm R=\rm La, low temperature ferromagnetic order for \rm R=\rm Ce, Pr, and paramagnetic character for \rm R=\rm Nd, respectively. SmAlSi shows metamagnetic transition at 10 K and ferromagnetic order at 143 K, respectively. SmAlSi follows the van Vleck paramagnetic model in its paramagnetic region. The magnetization curves of RAlSi (\rm R=\rm Ce, Pr, Sm) follow the mixed model of ferromagnetism and paramagnetism, and the fitted saturation moment M_\rm S depends on the moment of trivalent rare earth. The paramagnetic susceptibility \chi of RAlSi is going up with increasing the atomic order numbers of rare earth elements. This reveals that the magnetic property of RAlSi originates from the rare earth.