Magnetostructural phase transitions in manganese arsenide single crystals

Giant magnetocaloric effect in composites based on polymeric matrix and manganese arsenide

“…1 shows the MCE temperature dependencies in bulk MnAs obtained at adiabatic field excursion from zero to the value of 12.5 kOe in the region of magnetic phase transition. Curve 1 relates to the case where the sample was heated up from ferromagnetic state (T < 300 K) In second case (curve 2) the sample is cooled from paramagnetic state (T > 320 K) to room temperature, the MCE shows maximum value of ∆T = 0.88 K at temperature T = 306 K. Our data point to the fact that there are two metastable phase caused by transition from ferromagnetic to paramagnetic state [19]. As far as relative ratio of ferromagnetic and paramagnetic phases in the samples at heating and cooling is distinct, the MCE has different values depending on thermal history of the sample.…”

“…The maximum of MCE (∆T = 1.3 K) is reached at T C = 309 K for both cooling and heating. The MCE value in this composite is exceed the MCE in bulk MnAs at the same magnetic field [19]. It is quite possible that this behaviour is result of residual pressure of polymeric matrix pushed to MnAs grains [25].…”

“…One is magnetoelastic transition, in which no crystal symmetry evolution but the change of lattice parameters is observed on both sides of the phase transition, such as MnFeP 1−x As x and La(Fe,Si) 13 [13][14][15]. The other is magnetostructural transition (MST), in which magnetic and crystallographic transitions oc-EPJ Web of Conferences 185, 05010 (2018) https://doi.org/10.1051/epjconf/201818505010 MISM 2017 cur simultaneously, such as Gd 5 (Si 2 Ge 2 ), Mn-Ni-Ga(Fe) [16,17] and MnAs [18][19][20]. In these cases, relatively smaller thermal/magnetic hysteresis than those possessing magnetostructural transition are generally revealed.…”

“…It displays one of the highest MCE neighboring room temperature. At the Curie temperature (T C ) MnAs demonstrates the MST from low-temperature ferromagnetic hexagonal NiAs-type state to a high-temperature paramagnetic state with orthorhombic MnP-type crystal structure [19,24]. These MST and their concomitant entropy changes can be triggered by applying an external magnetic field [19,24] and by an external pressure [25] giving rise to the MCE.…”

“…At the Curie temperature (T C ) MnAs demonstrates the MST from low-temperature ferromagnetic hexagonal NiAs-type state to a high-temperature paramagnetic state with orthorhombic MnP-type crystal structure [19,24]. These MST and their concomitant entropy changes can be triggered by applying an external magnetic field [19,24] and by an external pressure [25] giving rise to the MCE. It was shown that both ferro-and paramagnetic metastable phase coexist in MnAs in the region of phase transition, and so the MCE is caused by field induced magnetic phase transition from paramagnetic to ferromagnetic state [19].…”