Pressure effect on magnetic phase transitions in slowly cooled NiMn1-xCrxGe

For a slowly cooled series of NiMn1-xCrxGe half-Heusler alloys (x = 0.04, 0.11, 0.18 and 0.25) the magnetostructural (P,T) phase diagrams, under hydrostatic pressure up to 13.5 kbar, were determined. At ambient pressure a magnetic (second order) transition and a structural (first order, martensitic) phase transition are observed. The temperature of the magnetic phase transition increases while the one of the structural phase transition decreases with increasing pressure. The lines of these dependences intersect at so-called triple point (PTRI, TTRI) and a magneto-structural (first order) phase transition develops with further pressure increase. The magneto-structural transition temperature decreases with increasing pressure. The value of the triple point pressure PTRI decreases with increasing Cr content, from about 8 kbar (for x = 0.04) to about 1 kbar (for x = 0.25) on heating.