Large reversible room-temperature magnetocaloric effect in the Ba0.5Sr1.5Zn2Fe12O22-related hexaferrites

Single-Crystal Growth and Room-Temperature Magnetocaloric Effect of X-Type Hexaferrite Sr2Co2Fe28O46

“…The former one is only ∼0.5 J/kg·K, but the latter is about 1.1 J/kg·K for Δ H = 5 T. The results indicate an anisotropic magnetocaloric effect induced by the significant magnetocrystalline anisotropy. The value of Δ S M for Sr 2 Co 2 X is slightly smaller than that observed in Y-type hexaferrites with Δ S M between ∼1.27 and ∼2.0 J/kg·K, , but larger than that in the W-type hexaferrite with Δ S M of ∼0.18 J/kg·K . It should be mentioned here that the M-type hexaferrite impurity may have some contribution to the magnetic properties of the sample, but it should have no contribution to the spin reorientation transition and the room-temperature magnetocaloric effect due to its higher transition temperature.…”

“…Ba can be partially or fully substituted by Sr . Recently, magnetocaloric effect (MCE) was identified in some hexaferrites, such as M-type BaFe 12‑ x Co x Ti x O 19 , W-type BaCo 0.62 Zn 1.38 Fe 16 O 27 , and Y-type Ba 0.3 Sr 1.7 Co 2 Fe 12 O 22 and Ba 0.5 Sr 1.5 Zn 2 Fe 12 O 22 -related hexaferrites. − In addition, the magnetoelectric (ME) coupling has been also reported in Y-, M-, W-, U-, and Z-type hexaferrites with special conical magnetic structure except the X-type analog. − Considering the similar structural features of different hexaferrites, it is natural to predict the X-type hexaferrites being the right candidates for ME materials. However, the high-quality samples of X-type hexaferrites are difficult to prepare, especially a single crystal with high quality and large size.…”