Rotating magnetocaloric effect in highly anisotropic TbIII and DyIII single molecular magnets

The magnetocaloric effect (MCE) was investigated in highly anisotropic single crystals of two single molecule magnets (SMMs): [Ln(III)((ZnL)-L-II)(2)]CF3SO3, 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 parallel to Zn-Ln-Zn array and a hard plane ab perpendicular to Zn-Ln-Zn array. The magnitude of MCE measured for c parallel to H was significantly greater than MCE for ab parallel to 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 mu H-0 = 1.3 T for Ln = Tb and 3.3 J K-1 kg(-1) at mu H-0 = 1.1 T for Ln = Dy. The relative efficiency of RMCE compared to the MCE measured in c parallel to H was as high as 99% at low magnetic fields.

Automated summary

The magnetocaloric effect was investigated in highly anisotropic single crystals of two single molecule magnets. It was found that the magnitude of the effect was greater when the magnetic field was applied perpendicular to the crystal structure. The rotating magnetocaloric effect was evaluated and found to have a high relative efficiency at moderate magnetic fields.