Variation of Tricritical Point of a Metamagnet with Dilution

Abstract

Tricritical point (TCP) of a dilute metamagnet is investigated by the Takagi approximation on the basis of Ising meta-model. It is shown that the tricritical temperature decreases when the system is diluted by non-magnetic atoms, and becomes zero at the concentration c_p, which coincides with the critical concentration of a ferromagnetic plane in the same approximation, despite of essentially three-dimensional nature of the metamagnetic transition. It is also shown that, in contrast to the tricritical temperature, the tricritical field tends to a finite value with dilution.
The results obtained agree qualitatively with the magneto-optical study of dilute metamagnet Fe_cMg_1−cCl₂ by Wood and Day.