Rotating magnetocaloric effect in highly anisotropic Tb III and Dy III single molecular magnets

The magnetocaloric effect (MCE) was investigated in highly anisotropic single crystals of two single molecule magnets (SMMs): [Ln III (Zn II L) 2 ]CF 3 SO 3 , where Ln = Tb, Dy and L = tripodal hexadentate Schiff base ligand. The structure of these paramagnetic compounds consists of identically oriented linear trinuclear clusters in a trigonal system with an easy direction c ∥Zn–Ln–Zn array and a hard plane ab ⊥Zn–Ln–Zn array. The magnitude of MCE measured for c ∥ H was significantly greater than MCE for ab ∥ H at a wide temperature range regardless of the studied SMM. Therefore, the rotating magnetocaloric effect (RMCE) was evaluated. The maxima of the magnetic entropy change for RMCE were obtained at 2.0 K and moderate fields: 3.9 J K −1 kg −1 at µ 0 H = 1.3 T for Ln = Tb and 3.3 J K −1 kg −1 at µ 0 H = 1.1 T for Ln = Dy. The relative efficiency of RMCE compared to the MCE measured in c ∥ H was as high as 99% at low magnetic fields.