Large Cryogenic Magnetocaloric Effect Research Articles

Structural, magnetic properties and large cryogenic magnetocaloric effect (MCE) in RE2MgTiO6 (RE = Tb, Dy, Ho and Er) double perovskite (DP) oxides

We have systematically studied the crystal structure, cryogenic magnetic properties and MCE in RE2MgTiO6 (RE = Tb, Dy, Ho and Er) DP oxides. The four RE2MgTiO6 samples are all found to crystallize in a monoclinic DP structure (P21/n space group). The Néel temperature (TN) are found to be 4.7, 4.5, 3.1 and 2.1 K for RE2MgTiO6 (RE = Tb, Dy, Ho and Er) DP oxides, respectively. Moreover, the maximum magnetic entropy change (-ΔSMmax) together with relative cooling power (RCP) near TN under a magnetic field change (ΔH) of 0–7 T are evaluted to be 16.85, 360.59 for Tb2MgTiO6, 17.72, 381.05 for Dy2MgTiO6, 15.92, 398.14 for Ho2MgTiO6 and 22.95 J/kg K, 459.09 J/kg for Er2MgTiO6, respectively. The excellent cryogenic MCE suggest that RE2MgTiO6 (RE = Tb, Dy, Ho and Er) DP oxides can be used as a promising candidate material for cryogenic magnetic refrigeration.

Borderline first-order phase transition and large cryogenic magnetocaloric effect in PrNdIn

We report a large cryogenic magnetocaloric effect stemming from an unconventional borderline first-order magnetic phase transition with negligibly small thermomagnetic hysteresis in a rare-earth-based intermetallic compound PrNdIn. The sample exhibits maximum magnetic field-induced entropy change as large as −10 J/Kg K (for 20 kOe magnetic field change) near the boiling point of oxygen. Magnetocaloric properties of PrNdIn are comparable to those of other known potential magnetocaloric materials with operating temperatures ranging between 50 and 125 K. The magnetic properties of the present sample are qualitatively reminiscent of those of the binary Pr2In and Nd2In, including the emergence of a second low-temperature anomaly in the temperature dependence of magnetization.

Excellent magnetocaloric performance in the carbide compounds RE2Cr2C3 (RE = Er, Ho, and Dy) and their composites

The rare earth (RE) based alloys or compounds with excellent cryogenic magnetocaloric performance have received much research interest recently due to their potential applications of environmental friend magnetic refrigeration (MR) technology. Herein, three ternary RE-based carbide compounds RE2Cr2C3 (RE = Er, Ho, and Dy) were synthesized, an investigation of combined experimental and theoretical has been performed with regard to crystal structure, magnetic properties, magnetic phase transition as well as the magnetocaloric effect (MCE) and magnetocaloric performance. All the RE2Cr2C3 carbide compounds are crystallized in the orthorhombic type crystal structure (C12/m1 space group). The magnetic ground state was confirmed to be ferromagnetic (FM) for Er2Cr2C3, whereas antiferromagnetic (AFM) for Ho2Cr2C3 and Dy2Cr2C3 compounds by density functional theory calculation in addition to experimental observation. Large cryogenic MCE has been observed with the maximum isothermal magnetic entropy change (-ΔSMmax) of 15.20, 13.98 and 9.04 J/kgK for Er2Cr2C, Ho2Cr2C3 and Dy2Cr2C3 under the magnetic field change (ΔH) of 0–5 T, respectively. Additionally, low field table-like MCE has been achieved in the Er2Cr2C3/Ho2Cr2C3 composites, which is benefit for active applications. These results assess and highlight the potential applicative interest of RE2Cr2C3 carbide compounds in the field of cryogenic MR.

Correlating Crystallography, Magnetism, and Electronic Structure Across Anhysteretic First-Order Phase Transition in Pr2In

Temperature-dependent powder X-ray diffraction and magnetization measurements of Pr2In conclusively prove that the unusual anhysteretic first-order paramagnetic-ferromagnetic phase transition in the compound is related to concurrent changes in both the magnetic and crystallographic lattices. At the same time, the hexagonal Ni2In-type structure is stable at least between 6 and 298 K, including at T C = ∼57 K. From the density functional theory calculations, the electronic structure of the compound is extraordinarily sensitive to minor changes in lattice parameters that occur across the phase transition, revealing the origin of strong magnetoelastic coupling. In the vicinity of T C, the maximum entropy change, ΔS Max = −16 J Kg−1 K−1 induced by a moderate magnetic field change of 20 kOe (ΔS Max = −20 J Kg−1 K−1 for 50 kOe magnetic field change) is comparable to other known potentially functional materials demonstrating large cryogenic magnetocaloric effect.

A two dimensional GdIII coordination polymer based on isonicotinic acid N‐oxide with large magnetocaloric effect

AbstractOne two‐dimensional (2D) GdIII coordination polymer based on isonicotinic acid N‐oxide (HINNO), {[Gd(INNO)2(HCOO)] ⋅ 2H2O}n (1), was successfully synthesized and characterized. Magnetic studies reveal the presence of weak antiferromagnetic couplings between adjacent GdIII ions in the 1D chain units of 1 and large cryogenic magnetocaloric effect with maximum −ΔSm of 31.84 J kg−1 K−1 at T=2 K and ΔH=7 T.

One trans-aconitate-based two-dimensional Gd(III) polymer displaying large magnetocaloric effect

One two-dimensional Gd(III) coordination polymer based on trans-aconitic acid (H3ANA) ligand, [Gd(ANA)(DMF)(H2O)2]n (1), was prepared solvothermally and characterized structurally. Single crystal X-ray diffraction analysis reveals that complex 1 crystallizes in monoclinic P21/c space group and possesses a 2D layer structure containing 3-connected Gd(III) ion and tridentate ANA3− ligand. The 2D structure owns a metal skeleton of co-edge parallelogram with the Gd⋯Gd distances of 8.36 (1) Å × 9.48 (1) Å. Magnetic studies demonstrate that 1 displays weak ferromagnetic interaction between the neighboring Gd(III) ions from the adjacent 2D layers, and has a large cryogenic magnetocaloric effect with the maximum −ΔSm value of 35.89 J kg−1 K−1 at 2 K and ΔH = 7 T.

Magnetic properties and large cryogenic magneto-caloric effect of Er0.2Tm0.2Ho0.2Cu0.2Co0.2 amorphous ribbon

In this paper, the glass forming ability (GFA), magnetic properties and magneto-caloric effect (MCE) performances in Er0.2Tm0.2Ho0.2Cu0.2Co0.2 amorphous ribbon were reported. A relatively big supercooled liquid region ~43.1 K and a broad typical ferromagnetic to paramagnetic phase transition around TC ~ 13.5 K accompanied by a large cryogenic MCE were observed in Er0.2Tm0.2Ho0.2Cu0.2Co0.2 amorphous ribbon. The magnetic entropy change peak and refrigerant capacity (relative cooling power) values in Er0.2Tm0.2Ho0.2Cu0.2Co0.2 amorphous ribbon for ΔH = 0–5 T are calculated to be 15.73 J/kgK and 354.3 (448.1) J/kg, respectively. The large MCE parameters together with good GFA, making the Er0.2Tm0.2Ho0.2Cu0.2Co0.2 amorphous ribbon is also attractive for cryogenic magnetic refrigeration (MR).

An exceptionally stable 3D GdIII-organic framework for use as a magnetocaloric refrigerant

The first example of a 3D GdIII-H4abtc framework was successfully prepared, exhibiting a large cryogenic magnetocaloric effect and exceptional air and chemical stabilities, especially in water and under acidic/alkaline conditions.

One-dimensional GdIII–MII (M = Mn, Co) acetate chains exhibiting a large cryogenic magnetocaloric effect at ΔH = 3 T

Two one-dimensional acetate chains, GdIII–MnII (1) and GdIII–CoII (2), have been prepared. Magnetic investigations indicate that the magnetic entropy changes in 1 and 2 are up to 38.70 and 35.18 J kg−1 K−1 at ΔH = 7 T, and 31.08 and 28.67 J kg−1 K−1 at ΔH = 3 T, respectively.

Gadolinium(III)‐Hydroxy Ladders Trapped in Succinate Frameworks with Optimized Magnetocaloric Effect

Two kinds of inorganic gadolinium(III)-hydroxy "ladders", [2×n] and [3×n], were successfully trapped in succinate (suc) coordination polymers, [Gd2(OH)2(suc)2(H2O)]n·2nH2O (1) and [Gd6(OH)8(suc)5(H2O)2 ]n·4n H2O (2), respectively. Such coordination polymers could be regarded as alternating inorganic-organic hybrid materials with relatively high density. Magnetic and heat capacity studies reveal a large cryogenic magnetocaloric effect (MCE) in both compounds, namely (ΔH=70 kG) 42.8 J kg(-1) K(-1) for complex 1 and 48.0 J kg(-1) K(-1) for complex 2. The effect of the high density is evident, which gives very large volumetric MCEs up to 120 and 144 mJ cm(-3) K(-1) for complexes 1 and 2, respectively.

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

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.

Increasing the dimensionality of cryogenic molecular coolers: Gd-based polymers and metal–organic frameworks

The magnetothermal properties of a coordination polymer and a metal-organic framework (MOF) based on Gd(3+) ions are reported. An equally large cryogenic magnetocaloric effect (MCE) is found, irrespective of the dimensionality. This combined with their robustness makes them appealing for widespread magnetic refrigeration applications.

Cryogenic Magnetocaloric Effect in a Ferromagnetic Molecular Dimer

Molecoolers: An unprecedentedly large cryogenic magnetocaloric effect is observed in gadolinium acetate tetrahydrate (see picture, Gd pink, O red, C gray). The change in its magnetic entropy is ascribed to the high magnetic density combined with dominant ferromagnetism. For the first time in a molecular complex, direct measurements of the magnetocaloric effect corroborate indirect estimates based on heat capacity and magnetization.

Formation and large cryogenic magnetocaloric effect of HoAl2/Al2O3 nanocapsules

HoAl2/Al2O3 nanocapsules with a core of HoAl2 and a shell of amorphous Al2O3 have been synthesized. The formation of the rare-earth compound nanocapsules can be ascribed to the different melting points and the optimal proportions of Ho and Al atoms during the arc-discharging process. Furthermore, the formation of the Al2O3 shell protects the rare-earth atoms from serious oxidation. The HoAl2/Al2O3 nanocapsules display superparamagnetic properties between the blocking temperature of 6 K and the Curie temperature of 26 K. The absolute value of the magnetic-entropy change in the HoAl2/Al2O3 nanocapsules rapidly increases with the decrease in temperature and reaches 14.7 J kg−1 K−1 at 3 K for a magnetic-field change from 0 to 70 kOe. As a result, this new type of nanocapsule may be applied, in the temperature range studied, in cryogenic magnetic-refrigerator devices.

Ce 3Al 11/Al 2O 3 nanocapsules with large cryogenic magnetocaloric effect

Nanocapsules with the intermetallic compound Ce 3Al 11 as core and amorphous Al 2O 3 (or Al) as the shell have been prepared using the arc-discharge technique. The Ce 3Al 11/Al 2O 3 nanocapsules display superparamagnetic properties between the blocking temperature and the Curie temperature. The cryogenic magnetocaloric effect of the Ce 3Al 11/Al 2O 3 nanocapsules was measured between 2 and 14 K. A maximum magnetic-entropy change −Δ S M of 8.3 J kg −1 K −1 has been observed at 4.5 K for a magnetic-field change from 0 to 70 kOe.

Large cryogenic magnetocaloric effect of DyCo2 nanoparticles without encapsulation

The structure and formation of nanoparticles without encapsulation of the intermetallic compound DyCo2 were investigated by using x-ray diffraction and high-resolution transmission electron microscopy. The DyCo2 nanoparticles are stable in air without any shell protection. A large magnetic-entropy change of 13.2Jkg−1K−1 was found at 7.5K in an applied-field change from 1to7T, which is ascribed to the large magnetic moment density and the weak interaction energy in the nanoparticles. Such oxidation-resistant rare-earth transition-metal compound nanoparticles with large cryogenic magnetocaloric effect are useful for refrigeration applications at low temperatures.

The large cryogenic magnetocaloric effect of TbAl 2 nanocapsules

TbAl 2 nanocapsules with a core of TbAl 2 compound and a shell of amorphous Al 2 O 3 were synthesized by the arc-discharge technique using modified strategies. The TbAl 2 nanocapsules display superparamagnetic properties between the blocking temperature of 70 K and the Curie temperature of 100 K. The absolute value of the change of magnetic entropy of the TbAl 2 nanocapsules rapidly increases with decreasing temperature, reaching 23.83 J kg −1 K −1 at 7.5 K with a magnetic field change of 70 kOe.

Synthesis of a new type of GdAl2 nanocapsule with a large cryogenic magnetocaloric effect and novel coral-like aggregatesself-assembled by nanocapsules

A new type of GdAl2 nanocapsule with single-phase intermetallic compoundGdAl2 as the core andamorphous Al2O3 as the shell has been synthesized by the arc-discharge technique with modified strategies. Meanwhile,novel three-dimensional coral-like hierarchical branching macro-aggregates were self-assembledby disordered nanocapsules synthesized simultaneously in the arc-discharge process. TheGdAl2 nanocapsules display superparamagnetic properties between their blocking temperatureof 100 K and Curie temperature of 162 K. The magnetocaloric effect of theGdAl2 nanocapsules was measured between 5 and 165 K. The absolute value of the change of magnetic entropyof the GdAl2 nanocapsules sharply increases with decreasing temperature and reaches14.5 J kg−1 K−1 at 5 K in magnetic fields varying from 0 to 50 kOe. As a result, this new type ofnanocapsule can prospectively be applied in cryogenic magnetic refrigerator devices.