Analysis of the magnetic transition and magnetocaloric effect in Mn5Ge2.9Ag0.1 compound

Large Anisotropic Magnetocaloric Effect, Wide Operating Temperature Range, and Large Refrigeration Capacity in Single-Crystal Mn5Ge3 and Mn5Ge3/Mn3.5Fe1.5Ge3 Heterostructures

“…Moreover, the −Δ S of these two materials is larger in the H // c case than in the H // a case as a result of their magnetic anisotropy. Under 0–3 T, the −Δ S max of the single crystal is 5.19 J kg –1 K –1 when H // c , larger than that of polycrystalline Mn 5 Ge 3 and other Mn 5 Ge 3 -based compounds. − ,− As the magnetic moments of Mn 3.5 Fe 1.5 Ge 3 are smaller than those of Mn 5 Ge 3 , the −Δ S max of the heterostructure is 2.96 J kg –1 K –1 under the same conditions, still comparable to that of Mn 5 – x (Fe,Co) x Ge 3 composites …”

“…However, the temperature dependence of magnetization shows that the heterostructure has two prominent magnetic transitions around 300 and 332 K, different from pure Mn 5 Ge 3 ( T C = 296–304 K) and other Mn 5 Ge 3 -based compounds with one prominent magnetic transition and without a structural transition below 400 K. − For clarifying the true compositions of the heterostructure, the microstructure and EDS mappings of the cross-section (incompletely vertical to the growth direction) of the crystal embedded in the Sn flux were characterized as shown in Figure a–g. The cross-section is surrounded by Sn, and little Sn is embedded at its center.…”

“…Mn 5 Ge 3 with a SOMT near RT possesses the hexagonal D8 8 -type structure (space group P 6 3 /mcm ) with two different crystallographic sites 4d (Mn I ) and 6g (Mn II ) for Mn atoms. Polarized neutron diffraction results suggested that single-crystal Mn 5 Ge 3 has a collinear ferromagnetic structure with two distinctive magnetic moments of 1.96 μ B /Mn I and 3.23 μ B /Mn II parallel to the c -axis at 4.2 K below its Curie temperature T C = 296 K. Songlin et al reported that polycrystalline Mn 5 Ge 3 has a maximum magnetic entropy change −Δ S max of 9.3 J kg –1 K –1 close to that of pure Gd under 0–5 T at T C = 298 K. In order to improve its magnetocaloric properties, several groups substituted Sb, Al, Si, or Ag for Ge. − Unfortunately, the Δ S decreases as well as the T C . There is another selection to substitute Mn with other magnetic elements to enhance its magnetocaloric properties.…”

Phenomenological Modeling of Thermomagnetic Properties and Magnetocaloric Effect of (Mn$$_{0.6}$$Fe$$_{0.4}$$)NiSi$$_{1-x}$$Al$$_{x}$$ ($$x = 0.07$$ and 0.08) Alloys

“…where B is the bulk elastic modulus and ΔV V is fractional change in unit cell volume [31]. It has been observed that a…”

Tuning of the Magnetocaloric Properties of Mn5Ge3 Compound by Chemical Modification

“…This compound, owing to its physical properties, may be used in magnetic refrigerators [39,40]. The attractive properties of Mn 5 Ge 3 initiated studies of, for example, off-stoichiometric Mn 5+x Ge 3-x alloys [41] or systems modified chemically by introducing elements such as Co [42][43][44][45], Fe [42,[44][45][46][47], or Ni [48] into the Mn position or by replacing Ge with Si [49,50], Ga [51], Sb [52], Al [53], Ag [54,55], or even Fe [56]. Moreover, simultaneous substitutions of Fe for Mn and Si for Ge have also been attempted [57,58].…”