Magnetic susceptibility anomaly connected with a displacive phase transition in MnAs1−xPx and CrxMn1−xas compounds

Some structural and magnetic properties of Mn1 + ΔAs1−xPx single crystals

“…In particular, a z -' ( T ) anomaly at TI occurs although there is no second-order NiAs-MnP transition reported here. Possibly, the x-' (T) anomaly simply reflects a magnetovolume effect U,(u); this would be consistent with the description of the first-order phase transition at T,, which is based on a strong dependence T,(u) [35], and would also allow to describe the x-( T ) anomaly by a temperature dependent pm Curie temperature tl,(T) [30]. It would remain to answer what causes the anomaly in aujaT: for stoichiometric crystals we cannot rule out a second-order NiAs-MnP phase transition as a cause, but with the (type I) crystals used here it is more likely that a distribution of (volume dependent) magnetic couplings O,(u) which extends x up to TI is responsible.…”

“…The magnetic state for T > T, has been described as Curie-Weiss paramagnetism. Below TI anomalies are observed in the magnetic susceptibility versus temperature curves [22 to 291 and were discussed using different approaches [30,311, but all of which assumed the paramagnetic state for T,, < T < TI.…”

A Mössbauer study of57Fe in MnAs

“…Anion substitution with phosphorous has the same effect as applying hydrostatic pressure to MnAs. Extensive studies of the system MnAs,-,P, for 0.00 < x < 0.18 have been carried out, partly focusing on the coupling of the spin conversion (1s cf hs) with the continuous structural MnP ++ NiAs-type transition, and partly considering the complicated helical magnetic structures found at low temperatures [12][13][14][15][16][17][18][19][20][21]. Furthermore, Zieba et al [22] reported that the spin and structural transition can be induced if a magnetic field is applied to MnAso,,P, o4 samples in its MnP-type helimagnetic mode (latent ferromagnetism).…”