Improving Thermal Cycling Stability and Magnetocaloric Efficiency via Orbital Competition and Entropy Engineering in Rare-Earth Rhodium Indium Layered Intermetallics

A series of RE 11 Rh 4 In 9 intermetallics ( RE = Gd, Tb, Ho, and Tm) adopting the Nd 11 Pd 4 In 9 -type structure (space group Cmmm, oS48) was synthesized. The structure of these compounds has been visualized and described through CsCl- and AlB 2 -type fragment tiling, with the help of in-house developed software, revealing the structure as an intermediate in the CsCl- to AlB 2 -type structure transformation with 18% of the AlB 2 -type fragments and no face sharing between these fragments. Magnetic properties of RE 11 Rh 4 In 9 ( RE = Gd, Tb) have been examined. The compounds undergo transition from para- to ferromagnetic order near 80 K with additional magnetic transitions detectable at lower temperatures. Magnetic entropy change reaches 5.32 and 3.66 J·kg –1 ·K –1 under a magnetic flux density change of μ 0 Δ H = 0–9 T for RE = Gd and Tb, respectively. Relative cooling power and refrigerant capacity are equal to 615.4 and 501.1 J·kg –1 in Gd 11 Rh 4 In 9 and 393.2 and 311.4 J·kg –1 in Tb 11 Rh 4 In 9 under μ 0 Δ H = 0–9 T. RE 11 Rh 4 In 9 establishes a structural family of Rh-containing rare-earth intermetallics that exhibit competitive magnetocaloric performance in a broad range with the maximum near 80 K. Subtle changes in the electronic structure govern exchange interactions and magnetic entropy for tuning magnetocaloric properties through controlled f – d hybridizations.