Transformation behavior and magnetocaloric effect in Mn1−xCrxCoGe (x = 0.04 and 0.11) melt-spun ribbons tailored by heat treatment

Giant and Reversible Inverse Barocaloric Effects near Room Temperature in Ferromagnetic MnCoGeB0.03

“…Using a Hitachi TM 3000 Tabletop scanning electron microscope, the formation of cracks was confirmed in a ribbon of MnCoGeB 0.03 (sample #3) that was fabricated by melt‐spinning under argon, as described in refs. . The ribbon did not require any polishing of the brittle specimen prior to microscopy.…”

“…By contrast, it is straightforward to generate large changes of hydrostatic pressure Δ p in order to drive giant barocaloric (BC) effects near nonisochoric magnetostructural phase transitions, and it is straightforward to exploit a fragmented BC working body by encapsulating it together with the pressure‐transmitting medium. Here we use variable‐pressure calorimetry to investigate giant BC effects in the well‐known MC material MnCoGeB 0.03 near the ≈290 K paramagnetic/hexagonal to ferromagnetic/orthorhombic phase transition (PM/H to FM/O). This transition is associated with a giant change of volume (≈4%) that causes this brittle material to undergo a complete mechanical failure that would be problematic in MC cooling devices .…”

“…Magnetometry, calorimetry, and scanning electron microscopy were performed on more than one sample (samples #1–3, see the Experimental Section) because of virgin effects and the mechanical breakdown that arose with thermal cycling . Measurements of low‐field magnetization in sample #1 during the first cooling run show that the PM/H‐FM/O transition is broad [ Figure a].…”

Study of dual-phase functionalisation of NiCoFeCr-Alx multicomponent alloys for the enhancement of magnetic properties and magneto-caloric effect

“…However, there is a trade-off: thermal hysteresis leads to significant energy losses in the refrigeration cycle. FOPT materials also possess poor mechanical stability; the materials tend to fracture due to the stress induced (up to 4% volume change) during the crystallographic phase transition [6] [7]. To date the preferred materials for magnetic refrigeration demonstrate SOPT.…”

“…TC graded materials can be obtain either by stimulating a phase separation during the fabrication/post-annealing [1][10] treatment or by designing a composite of constituents each with a different TC [2] [11]. However, as ΔSm and TC tuning are highly sensitive to parameters such as elemental composition [7][12], microstructure variations [13] [14], and post-annealing treatment [6][15] [16], translating these experiments from a highly controlled lab-based research environment into a production line is an extremely difficult task.…”