Magnetic properties and local atom distributions in Mn19.8-xSn0.2Fex alloys with a β-Mn structure

The iron distribution among the nonequivalent 8c and 12d positions in Mn 19.8-x Sn 0.2 Fe x alloys (x = O to 22) with a β-Mn structure was investigated by 57 Fe Mossbauer spectroscopy. In the concentration range of interest, Fe atoms predominantly substitute for manganese atoms in 8c positions. An increase in iron concentration is accompanied by an increase in the number of Fe atoms substituting for manganese atoms in 12d positions. The susceptibility-vs-temperature curves of β-Mn 19.8-x Sn 0.2 Fe x exhibit anomalies related to the transition to a spin glass state. The temperature at which these anomalies occur rises as the amount of iron present in solid solution increases. The observed rise in the magnetic ordering temperature is ascribed to the suppression of frustrations of the magnetic moments of Mn atoms in 12d positions. This is additionally promoted by the increase in the number of manganese atoms that have a magnetic moment in 8c positions.