Effect of pressure on the curie points of the pseudo‐NiAs‐type Mn 1+δ Sn

Curie temperatures of Mn 1+δ Sn, including interstitial Mn atoms in NiAs‐type structure, have been investigated using the magnetic induction method at hydrostatic pressures up to about 5 kbar. The magnetic induction smoothly diminishes at T c (250 to 260 °K). No transition anomaly has been observed in electrical resistivity of Mn 1.77 Sn and Mn 1.5 Sn quenched from about 700°C. The values of specific resistivity are observed to be (4 ± 1) × 10 −4 Ωcm at room temperature. The Curie temperatures increase linearly with increasing pressure at the rates of d T c /d p : +(2.0 ± 0.1) deg/kbar, +(1.5 ± 0.1) deg/kbar, and +(1.2 ± 0.1) deg/kbar for Mn 1.77 Sn quenched from 710, 480, and 380°C, respectively, and +(1.9 ± 0.1) deg/kbar for Mn 1.5 Sn quenched from 700°C. The positive pressure effect indicates that the exchange interaction is enhanced by decreasing the volume in Mn 1+δ Sn. This deduces that the shift of T c due to change of quenching temperature is explicable in terms of the volume effect of exchange interactions. It is also found that d T c /dp strongly depends on the quenching temperature, i.e. the ordered arrangements of Mn interstitial atoms, although little difference has been observed in d T c /d p between δ = 0.5 and 0.77 quenched from about 700°C.