Evidence for temperature dependent moments ordering in ferromagnetic NiMnSb(100)

From magnetic circular dichroism measurements of the Heusler alloy NiMnSb, in combination with other techniques, we show that a dramatic increase in the Mn and Ni moments occurs below a ``crossover'' transition temperature of about 80--100 K. This phase transition is well below the Curie temperature of NiMnSb ({~}730 K). While the spin polarization near the Fermi level, from spin-polarized inverse photoemission, remains very high for k_∥=0, it is unlikely that NiMnSb is a half-metallic ferromagnet near room temperature.