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Abstract:
This work reports on the electronic, magnetic, and structural properties
of the binary intermetallic compounds Mn(3-x)Ga. The tetragonal DO(22)
phase of the Mn(3-x)Ga series, with x varying from 0 to 1.0 in steps of
x = 0.1, was successfully synthesized and investigated. It was found
that all these materials are hard magnetic, with energy products ranging
from 10.1 kJ m(-3) for low Mn content (x -> 1) to 61.6 kJ m(-3) for high
Mn content (x -> 0). With decreasing Mn content, the average saturation
magnetization per atom increases from 0.26 mu(B) for Mn(3)Ga to 0.47
mu(B) for Mn(2)Ga. The increase in the saturation magnetization as the
Mn content is reduced indicates a ferrimagnetic order with partially
compensating moments of the two different Mn atoms on the two
crystallographically different sites of the DO(22) structure. This type
of magnetic order is supported by ab initio calculations of the
electronic structure that predict a nearly half-metallic ferrimagnet
with the highest spin polarization of 88% at the Fermi energy for
Mn(3)Ga. The Curie temperature of the compounds is restricted to
approximately 770 K because of a structural phase transition to the
hexagonal DO(19) phase. Thermal irreversibilities between
zero-field-cooled and field-cooled measurements suggest that the
Mn(3-x)Ga series belongs to the class of magnetically frustrated
ferrimagnets. The most pronounced magnetic anomaly is found for Mn(3)Ga.
