A large cryogenic magnetocaloric effect exhibited at low field by a 3D ferromagnetically coupled Mn(ii)–Gd(iii) framework material

Abstract

The large cryogenic magnetocaloric effect of a 3D oxydiacetate-bridged gadolinium-manganese MOF material, [Mn(H(2)O)(6)][MnGd(oda)(3)](2)·6H(2)O (1), was evaluated by magnetization and heat capacity measurements. A maximum -ΔS(m) of 50.1 J kg(-1) K(-1) for ΔH = 70 kG along with significant entropy change at lower field was found on account of the weak Mn···Gd ferromagnetic interactions and the small molecular mass. This suggests that 1 could be considered as a potential coolant for liquid helium temperature applications.

A Dense Metal–Organic Framework for Enhanced Magnetic Refrigeration

“…[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.…”

“…[11][12][13][14][15] Indeed, the dimensionality of Gd-MOFs has no effect in itself on the MCE, bar its intrinsic density. Light and short bridging ligands, such as the formate ion, are clearly advantageous in this regard.…”

Magnetocaloric Properties of Heterometallic 3d–Gd Complexes Based on the [Gd(oda)3]3− Metalloligand

“…[2] Since the first report on the MCE in {Mn 12 }, [3a] many MC molecular clusters and coordination polymers were discovered. On the other hand, the reported 3d-4f magnetic coolantsi nclude various3 dt ransition metal ions, such as Mn 2 + , [5] Co 2 + , [6] Ni 2 + , [7] and Cu 2 + . In such systems, the 4f Gd 3 + ion is usually selected as ag ood candidate due to its high-spins tate (S = 7/2) and isotropy.…”

Magnetocaloric effect and thermal conductivity of Gd(OH)3 and Gd2O(OH)4(H2O)2

“…The magnetization of 1 and 2 increases steadily with the applied field and reaches 6.99 Nm B for 1 and 13.65 Nm B for 2 at 2 K and 7 T, in agreement with the calculated value of 7 Nm B for 1 and 14 Nm B for 2 respectively. 10 It was mentioned that the gravimetric entropy change larger than 50 J kg À1 K À1 at 2 K and DH = 7 T has only been observed in four compounds (Table 1), 4,5,17,18 while the volumetric entropy change larger than 210 mJ cm À3 K À1 has only observed in three compounds so far (including in the commercial magnetic refrigerant GGG 19 ), despite the great many efforts made. 11 As shown in Fig.…”