Giant and time-dependent magnetocaloric effect in high-spin molecular magnets

Abstract

We have measured and calculated the magnetocaloric effect in macroscopic samples of oriented high-spin molecular clusters like Mn 12 and Fe 8 as a function of the temperature and both the intensity and the sweeping rate of the applied magnetic field.We have observed a high magnetic entropy variation around the blocking temperature of the magnetic moment of molecules and calculated the shift of the entropy variation and cooling temperature, with the sweeping rate of the magnetic field.

A Dense Metal–Organic Framework for Enhanced Magnetic Refrigeration

“…[ 19 ] The single-crystal structure determination of Gd(HCOO) 3 is reported here, completing the original powder diffraction study. Our detailed magnetic and thermal studies allow direct and indirect estimation of its MCE and show that, while presenting a sub-Kelvin ordering temperature, Gd(HCOO) 3 indeed possesses a huge MCE, positioning this material in an enviable position within this research area.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Refrigeration proceeds adiabatically via the magnetocaloric effect (MCE), which describes the changes of magnetic entropy ( Δ S m ) and adiabatic temperature ( Δ T ad ), following a change in the applied magnetic fi eld ( Δ B ). As in the fi rst paramagnetic salt that permitted sub-Kelvin temperatures to be reached in 1933, [ 16 ] gadolinium is often present because its orbital angular momentum is zero and it has the largest entropy per single ion.…”

“…Light and short bridging ligands, such as the formate ion, are clearly advantageous in this regard. We therefore focus here on gadolinium formate, Gd(HCOO) 3 , a dense MOF material, characterized by a relatively high packing density of Gd 3 + ions, linked only through lightweight formate ligands, whose structure was originally determined on powder specimens. [ 17 , 18 ] Surprisingly, no previous magnetic measurements on Gd(HCOO) 3 are reported in the literature, except for initial Mössbauer experiments.…”

“…We therefore focus here on gadolinium formate, Gd(HCOO) 3 , a dense MOF material, characterized by a relatively high packing density of Gd 3 + ions, linked only through lightweight formate ligands, whose structure was originally determined on powder specimens. [ 17 , 18 ] Surprisingly, no previous magnetic measurements on Gd(HCOO) 3 are reported in the literature, except for initial Mössbauer experiments. [ 19 ] The single-crystal structure determination of Gd(HCOO) 3 is reported here, completing the original powder diffraction study.…”

“…Single crystals of Gd(HCOO) 3 were grown by allowing a solution of Gd(NO 3 ) 3 · 5H 2 O (0.5 g, 1 mmol), formic acid (15 mL), and H 2 O (10 mL) to evaporate slowly over several days. The product was collected as a crystalline solid and dried under vacuum ( > 90% yield) and analyzed satisfactorily (Anal.…”