What is the reason of magnetism in Heusler alloy when none of its constituents are magnetic such as Cu2MnAl? And how it is different than other Heusler alloy such as Co2FeAl.
Why do you think that constituent atoms in Cu2MnAl and Co2FeAl are not magnetic? Mn and Fe can be easily magnetic in metallic environment.
Sir, I am talking about Cu2MnAl in which none its constituent atom is ferromagnetic but the whole alloy can be . I agree with you as you replied me that Mn can be easily magnetic in metallic environment. What is the reason of ferromagnetism in Cu2MnAl and how it is different from Co2FeAl alloy in which Co and Fe are ferromagnetic.
Hi! Although Mn is not a ferromagnetic metal, Mn compounds can become ferro or antiferromagnetic based on the exchnage interactions of the Mn 3d electrons with their surrounding atoms. I am not exactly aware of the mechanism for the Cu2MnAl compounds but I work with other Mn based ferromagnetic half metallic systems and in their case there are mixed valence phase of Mn exists and the exchange interaction between the Mn3+ and Mn4+ through an intermediary oxygen (Mn3+-O-Mn4+) leads to ferromagnetism. Also compounds like GaMnAs shows ferromagnetism and there are lots of other examples also where Mn carrying compounds show ferromagnetism. Please search for literature and I think you'll find some papers when the exchange interaction of Cu2MnAl will be described in detail.
Mn of course is ferromagnetic. However the distance between MN atoms play a roll. In Heusler alloys the distance bet Mn atoms is such that it becomes ferromagnetic. Connsult a good text book on Mangetism.
The mechanisms responsible for the formation of magnetic moments in Heusler alloys was described by J. Kübler in 1983:
Formation and coupling of magnetic moments in Heusler alloys
J. Kübler, A. R. William, and C. B. Sommers
Phys. Rev. B 28, 1745 – Published 15 August 1983
On alloying, the exchange energy can become positive and the spins on neighbouring atoms can become aligned if the Mn–Mn distance is increased by the right amount, so that the ratio of the atomic diameter to the 3d orbital diameter falls in the range 1.5–2.0. This happens in Heusler alloys Cu2MnSn and Cu2MnAl, which are ferromagnetic.
- Badges
- Science topic