I am looking to see if transition between antiferromagnetic and ferromagnetic orders are possible. I'm looking for something akin to the ferro-para transition at the Curie point.
Alternatively, are there structures, such as exchange bias stacks that would allow for transition from an ordered ferromagnetic to another ordered state (either ferromagnetic with a different axis or antiferromagnetic).
FeRh alloy is an example of the material with antiferro-ferromagnet transition (Journal of Magnetism and Magnetic Materials, Volume 131, Issue 3, 2 March 1994, Pages 339–344).
Thank, Karol. This looks exactly like what I was hoping for. Rh seems to be rather expensive, but science is rarely cheap, no? Thanks for the heads up.
Such phase transitions from antiferromagnetic to ferromagnetic state are called metamagnetic transitions. Typically they take place in bulk rare-earth compounds as function of applied magnetic field. Other example are FeIrRh alloys, where AF-F transitions occur as function of temperature just above the room temperature.
I'll check into the MnCoNiFeP system - thanks, Hlil. Do you have any ideal on the change in moment across the transition? The FeRh system seems to have a rather high moment in the FM state.
Konstantin - I've been looking into the FeRh system, per Zaleski's suggestion. I'll check more generally in the metamagentic transition literature.
Thanks for the suggestions.
I assume the critical temperature can be tuned through composition? Is the MnCoNiFeP system available in bulk? It has the signature of an amorphous alloy composition.
80 emu/g is attractive - hopefully I could design to saturate before 2T.?
The Fe magnetic moment in FeRh (CsCl structure) was determined by neutron diffraction long time ago, see:
G. Shirane et al., Physical Review 131 (1963) 183, and a follow-up paper in 1964.
Eptaxial thin films of FeRh(001) on MgO(001) show an interesting Fe spin reorientation, see:
C. Bordel et al., Phys. Rev. Lett. 109, 117201 (2012).
Yes, the FeRh system is beautifully applicable to what I need. There is a group at North Eastern University (Dr. Lewis) still working in the system very actively - the rhodium is troubling commercially. I've consumed a good deal of literature on the system - it's been around for some time, as you point out. I was VERY excited to see that it works well in bulk. So many of these transitions seem to favor extreme mateiral configurations - like thin films or nanoparitcles.
Another exmaple not mentioned yet is Ni-Mn-Co-In showing a transition from a weakly F to stron F Transition. This material is considered as a material for magnetocalorics.
(Appl. Phys. Lett. 97, 222507 (2010); http://dx.doi.org/10.1063/1.3517443 )
The paper "The antiferromagnetic-ferromagnetic transition in iron-rhodium alloys" by J. B. McKINNON, D. MELVILLE and E. W. LEE was published in 1969 and is a classic example for antiferro-ferro transition. The paper also explains the reason for this transition.
As already mentionned, this is also observed in pure rare earth. For example Dysprosium is helimagnetic between 90 and 180K, but is ferromagnetic below 90 K. The antiferro-ferro transition happnes upon cooling, and not warming like for FeRh.
Cadmium ferrite at nano regime has several interesting transitions. You may try this. There are numbers of papers published on this material.
Essentially, any antiferromagnetic material becomes ferromagnetically ordered in strong enough external field, at fixed temperature, naturally. But I guess it's not what you are asking for.
Marek, I don't think my external field will be that high - lest than 1T. So, in a narrow field range, of 0-1T, I'm looking for first order transitions from AFM to FM. I need to avoid paramagnetic.
FeRh is a great option - except for the cost of the rhodium. I'm looking into some of the other systems, but I'm looking for a transition temperature in the 270-370K temperature range.
There should essential internal energy decrease in course of any AFM->FM transition increasing temperature because FM state has lower entropy in comparison to AFM one.
Konstantin - I am looking for a sharp transition between FM and AFM. Whether it goes AFM->FM or FM->AFM is not important. But, I like the first order change that is very sharp in temperature.
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