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.