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The analysis of specific heat, magnetic susceptibility and magnetization identified the studied compound Cu[C 6 H 2 (COO) 4 ][H 3 N–(CH 2) 2 –NH 3 ]·3H 2 O as a quasi-two-dimensional S = 1/2 Heisenberg antiferromagnet on the rectangular lattice with the intrachain coupling J 1 /k B ≈ 7.39 K and the interaction ratio R ≈ 0.44. A phase transition to a magnetically ordered state was observed in zero magnetic field at T N = 1.28 K. The analysis of magnetic specific heat in non-zero magnetic fields revealed features characteristic of the field-induced Berezinskii-Kosterlitz-Thouless phase transition theoretically predicted for ideal two-dimensional magnets. The electron paramagnetic resonance studies of Cu[C 6 H 2 (COO) 4 ][H 3 N–(CH 2) 2 –NH 3 ]·3H 2 O revealed the increase of g x and g y and decrease of g z below 25 K due to the presence of dipolar coupling and the exchange anisotropy. The upturn of linewidth appearing below 30 K can be ascribed to the development of intralayer magnetic correlations. • The system represents S = 1/2 Heisenberg antiferromagnet on the rectangular lattice. • A phase transition to a magnetically ordered state occurs in B = 0 T at T N = 1.28 K. • The field-induced Berezinskii-Kosterlitz-Thouless phase transition was observed. [ABSTRACT FROM AUTHOR]

Chain-like crystal structure of phenylacetato complex of Ce(III) elucidated by Rietveld method. Nona-coordinated Ce(III) ion (O 9 donor set) of muffin shape polyhedron. Field induced slow magnetic relaxation with direct and Raman relaxation processes. [Display omitted] [Ce(PAA) 3 (H 2 O)] n complex (1) (HPAA is phenylacetic acid) was synthesised and studied. The crystal structure of 1 was elucidated by the Rietveld method. Its crystal structure is polymeric and is built up of Ce(III) ions interconnected by bridging PAA− ligands. The Ce(III) ions in 1 are nona-coordinated by eight carboxylate oxygen atoms from six PAA− ligands, and one aqua ligand completes the coordination sphere yielding O 8 O donor set. The studied material displays field-induced slow magnetic relaxation. Temperature dependence of the relaxation time suggests the existence of direct and Raman relaxation processes. Similarly, as for the other Ce(III) complexes, the existence of Orbach process may be questioned due to the large discrepancy between the value of the energy gap obtained from static and dynamic measurements. [ABSTRACT FROM AUTHOR]

The magnetic properties of the hybrid materials formed by coordination compounds and clay minerals represent one of the main challenges in material science. The investigation of the intercalation of tris (2,2′-bipyridine)nickel(II) cations [Ni(bpy) 3 ]2+ present in the solution with chloride anions into synthetic saponite (Sap) was carried out by direct exchange of the sodium ions by nickel(II) complex. The final intercalated [Ni(bpy) 3 ]2+ saponite complex was characterized by powder X-ray diffraction (XRD), infrared (IR) spectroscopy, carbon and thermal analysis, and for the first time also by magnetic measurements. The carbon analysis proved a full replacement of Na+ with [Ni(bpy) 3 ]2+ cations. Furthermore, significant increase of the d 001 value of the intercalated saponite confirmed the presence of the [Ni(bpy) 3 ]2+ in Sap interlayers. Only limited effect of the saponite layers on the ring C-H or skeletal vibrations of the [Ni(bpy) 3 ]2+ complex was observed. The thermal stability of the [Ni(bpy) 3 ]2+ increased after its intercalation into saponite. The magnetic properties of the [Ni(bpy) 3 ]2+ saponite complex revealed similar magnetic response as the starting compound [Ni(bpy) 3 ]Cl 2 · n H 2 O suggesting that the local surroundings of the Ni(II) atoms in [Ni(bpy) 3 ]2+ intercalated into saponite remained unchanged. • The intercalation of [Ni(bpy) 3 ]2+ complex into synthetic saponite was accomplished. • The increase of d-value confirmed its presence in the saponite interlayers. • Thermal stability of the complex increased after its intercalation. • Magnetic properties of [Ni(bpy) 3 ]2+ remained unchanged after intercalation into saponite. [ABSTRACT FROM AUTHOR]

In our work, we have investigated the magnetocaloric effect (MCE) of core@shell Co@Au nanoparticles by heat capacity C p measurement in temperature range 1.9–55 K under external magnetic field. After the subtraction of lattice heat capacity contribution, the maximum of isothermal magnetic entropy change ΔS m   = 3.11 J K −1 kg −1 was obtained at field change from 0 to 9 T. Adiabatic temperature change ΔT ad   =  3.31 K, refrigerant capacity power RCP = 88.9 J kg −1 and efficiency of adiabatic temperature change η  = 0.37 K/T at the same external magnetic field change were established for the investigated system. The comparison of the results to the independent magnetic measurements data revealed the accordance of fundamental magnetocaloric characteristics obtained by both methods. Thus, this work is also the first experimental confirmation of relation between magnetocaloric response of nanoparticles and the low temperature magnetic transition from superparamagnetic to blocking/freezing state. [ABSTRACT FROM AUTHOR]

Organo-metallic compounds Cu( en )(H 2 O) 2 SO 4 ( en =C 2 H 8 N 2 ) and Cu( tn )Cl 2 ( tn =C 3 H 10 N 2 ) representing S =1/2 quasi-two-dimensional Heisenberg antiferromagnets with an effective intra-layer exchange coupling J/ k B ≈3 K, have been examined by specific heat measurements at temperatures down to nominally 50 mK and magnetic fields up to 14 T. A comparative analysis of magnetic specific heat in zero magnetic field revealed nearly identical contribution of short-range magnetic correlations and significant differences were observed at lowest temperatures. A phase transition to long-range order was observed in Cu( en )(H 2 O) 2 SO 4 at T C =0.9 K while hidden in Cu( tn )Cl 2 . A response of both compounds to the application of magnetic field has rather universal features characteristic for a field-induced Berezinskii–Kosterlitz–Thouless transition theoretically predicted for ideal two-dimensional magnets. [ABSTRACT FROM AUTHOR]