Separation of magnetic properties at uranium and cobalt sites in UCoAl using soft x-ray magnetic circular dichroism

Temperature (T) and magnetic field (H) dependence of the magnetic properties in metamagnetic UCoAl have been investigated using a soft x-ray magnetic circular dichroism (XMCD). In order to extract element-specific magnetic properties at the U and Co sites, the XMCD experiment has been performed at the U 4d-5f (N4,5) and Co 2p-3d (L2,3) absorption edges, respectively. Directions of magnetic moments at the U and Co sites have been determined from shapes of the XMCD spectra. The directions of the total magnetic moments at the U and Co sites are parallel to the H direction (c axis), but the direction of the spin magnetic moment at the U site is opposite to that at the Co site. The XMCD intensities at both the U and Co sites at T=5.5 K increase steeply at H=0.77 T (Hm), corresponding to the metamagnetic transition. The XMCD intensities do not saturate, even in the field-induced ferromagnetic state above Hm. In addition, the ratio of the increase of the XMCD intensity at the Co site is smaller than that at the U site. From comparison of the H dependence of the XMCD intensities at T=25 and 5.5 K, we found that the magnetic behavior of the Co atom has a stronger T dependence than that of the U atom. © 2013 American Physical Society