scholarly journals Insights into Nature of Magnetization Plateaus of a Nickel Complex [Ni4(μ-CO3)2(aetpy)8](ClO4)4 from a Spin-1 Heisenberg Diamond Cluster

2020 ◽  
Vol 6 (4) ◽  
pp. 59
Author(s):  
Katarína Karl’ová ◽  
Jozef Strečka ◽  
Jozef Haniš ◽  
Masayuki Hagiwara
Keyword(s):  
Low Temperature ◽  
Saturation Magnetization ◽  
Nickel Complex ◽  
Valence Bond ◽  
Entropy Change ◽  
Coupling Constants ◽  
Antiferromagnetic Coupling ◽  
Local Conservation ◽  
Low Temperature Refrigeration ◽  
Diamond Cluster

Magnetic and magnetocaloric properties of a spin-1 Heisenberg diamond cluster with two different coupling constants are investigated with the help of an exact diagonalization based on the Kambe’s method, which employs a local conservation of composite spins formed by spin-1 entities located in opposite corners of a diamond spin cluster. It is shown that the spin-1 Heisenberg diamond cluster exhibits several intriguing quantum ground states, which are manifested in low-temperature magnetization curves as intermediate plateaus at 1/4, 1/2, and 3/4 of the saturation magnetization. In addition, the spin-1 Heisenberg diamond cluster may also exhibit an enhanced magnetocaloric effect, which may be relevant for a low-temperature refrigeration achieved through the adiabatic demagnetization. It is evidenced that the spin-1 Heisenberg diamond cluster with the antiferromagnetic coupling constants J1/kB = 41.4 K and J2/kB = 9.2 K satisfactorily reproduces a low-temperature magnetization curve recorded for the tetranuclear nickel complex [Ni4(μ-CO3)2(aetpy)8](ClO4)4 (aetpy = 2-aminoethyl-pyridine) including a size and position of intermediate plateaus detected at 1/2 and 3/4 of the saturation magnetization. A microscopic nature of fractional magnetization plateaus observed experimentally is clarified and interpreted in terms of valence-bond crystal with either a single or double valence bond. It is suggested that this frustrated magnetic molecule can provide a prospective cryogenic coolant with the maximal isothermal entropy change −ΔSM=10.6 J·K−1·kg−1 in a temperature range below 2.3 K.

Relation between Magnetic, Spectroscopic and Structural Properties of Binuclear Copper(II) Complexes of Pentadentate Schiff-base Ligand, Semi-empirical and ab-initio Calculations

2003 ◽  
Vol 58 (5-6) ◽  
pp. 363-372 ◽  
Author(s):  
Y. Elerman ◽  
H. Kara ◽  
A. Elmali
Keyword(s):  
Ab Initio ◽  
Coupling Constants ◽  
Antiferromagnetic Coupling ◽  
X Ray Diffraction ◽  
Hartree Fock ◽  
Ligand Orbital ◽  
Rhf Calculations ◽  
The Difference ◽  
Semi Empirical

The synthesis and characterization of [Cu2(L1)(3,5 prz)] (L1=1,3-Bis(2-hydroxy-3,5-chlorosalicylideneamino) propan-2-ol) 1 and of [Cu2(L2)(3,5 prz)] (L2=1,3-Bis(2-hydroxy-bromosalicylideneamino) propan-2-ol) 2 are reported. The compounds were studied by elemental analysis, infrared and electronic spectra. The structure of the Cu2(L1)(3,5 prz)] complex was determined by x-ray diffraction. The magnetochemical characteristics of these compounds were determined by temperaturedependent magnetic susceptibility measurements, revealing their antiferromagnetic coupling. The superexchange coupling constants are 210 cm−1 for 1 and 440 cm−1 for 2. The difference in the magnitude of the coupling constants was explained by the metal-ligand orbital overlaps and confirmed by ab-initio restricted Hartree-Fock (RHF) calculations. In order to determine the nature of the frontier orbitals, Extended Hückel Molecular Orbital (EHMO) calculations are also reported.

Large magnetic entropy change at cryogenic temperature in rare earth HoN nanoparticles

RSC Advances ◽  
2016 ◽  
Vol 6 (79) ◽  
pp. 75562-75569 ◽  
Author(s):  
K. P. Shinde ◽  
S. H. Jang ◽  
M. Ranot ◽  
B. B. Sinha ◽  
J. W. Kim ◽  
...  
Keyword(s):  
Rare Earth ◽  
Low Temperature ◽  
Magnetocaloric Effect ◽  
Cryogenic Temperature ◽  
Magnetic Entropy Change ◽  
Entropy Change ◽  
Environmental Problems ◽  
Magnetic Refrigeration ◽  
Magnetic Entropy ◽  
Alternative Technology

The most extensive cooling techniques based on gases have faced environmental problems. The magnetic refrigeration is an alternative technology based on magnetocaloric effect. HoN nanoparticles are good refrigerant material at low temperature.

scholarly journals LOW-TEMPERATURE SYNTHESIS OF SUPERPARAMAGNETIC Zn0.8Ni0.2Fe2O4 FERRITE NANOPARTICLES

2018 ◽  
Vol 56 (1) ◽  
pp. 31
Author(s):  
Luong Thi Quynh Anh ◽  
Nguyen Van Dan ◽  
Do Minh Nghiep
Keyword(s):  
Particle Size ◽  
Magnetic Properties ◽  
Oleic Acid ◽  
Low Temperature ◽  
Coercive Force ◽  
Saturation Magnetization ◽  
Ferrite Nanoparticles ◽  
Low Temperature Synthesis ◽  
Temperature Synthesis ◽  
Co Precipitation

The crystalline nanoparticles of Ni0.2Zn0.8Fe2O4 ferrite were synthesized by chemical co-precipitation with precursor concentration of 0.1M, then modified by 0.25M solution of oleic acid in pentanol, finally heated at temperatures 120, 140, 160 and 180oC for 6h in autoclave. The XRD, EDS and TEM confirmed that all of samples are crystalline and their particle size are 6, 6.5, 7 and 8 nm. The magnetic properties showed that the coercive force, the remanence of samples are about zero, the saturation magnetization Ms has values from 14.20 to 27.12 emu/g.

scholarly journals Low-temperature antiferromagnetism of Ising model with competing interactions

2021 ◽  
pp. 64-71
Author(s):  
Kirill Tsiberkin ◽  
Keyword(s):  
Ising Model ◽  
Low Temperature ◽  
Temperature Shift ◽  
Second Order ◽  
Square Lattice ◽  
Antiferromagnetic Coupling ◽  
Competing Interactions ◽  
Saturation State ◽  
Spin Configuration ◽  
Competing Interaction

The paper presents a numerical analysis of equilibrium state and spin configuration of square lattice Ising model with competing interaction. The most detailed description is given for case of ferromagnetic interaction of the first-order neighbours and antiferromagnetic coupling of the second-order neighbours. The numerical method is based on Metropolis algorithm. It uses 128×128 lattice with periodic boundary conditions. At first, the simulation results show that the system is in saturation state at low temperatures, and it turns into paramagnetic state at the Curie point. The competing second-order interaction makes possible the domain structure realization. This state is metastable, because its energy is higher than saturation energy. The domains are small at low temperature, and their size increases when temperature is growing until the single domain occupies the whole simulation area. In addition, the antiferromagnetic coupling of the second-order neighbours reduces the Curie temperature of the system. If it is large enough, the lattice has no saturation state. It turns directly from the domain state into paramagnetic phase. There are no extra phases when the system is antiferromagnetic in main order, and only the Neel temperature shift realizes here.

scholarly journals Magnetic and microwave absorbing properties of low-temperature sintered BaZrxFe(12−x)O19

RSC Advances ◽  
2018 ◽  
Vol 8 (73) ◽  
pp. 42009-42016 ◽  
Author(s):  
Li Deng ◽  
Yang Zhao ◽  
Zhaoming Xie ◽  
Zuohua Liu ◽  
Changyuan Tao ◽  
...  
Keyword(s):  
Low Temperature ◽  
Saturation Magnetization ◽  
High Saturation Magnetization ◽  
Microwave Absorbing Properties ◽  
High Saturation ◽  
Microwave Absorbing

BaZrxFe(12−x)O19 ferrites synthesized at low temperature have high saturation magnetization, a wide coercivity range and excellent microwave absorbing properties.

A low-temperature study of the magnetic properties of the molecular cations O2+, Br2+, and I2+

1989 ◽  
Vol 67 (11) ◽  
pp. 1942-1948 ◽  
Author(s):  
M. S. R. Cader ◽  
R. C. Thompson ◽  
F. Aubke
Keyword(s):  
Magnetic Properties ◽  
Low Temperature ◽  
Magnetic Moment ◽  
Photoelectron Spectroscopy ◽  
Theoretical Models ◽  
Antiferromagnetic Coupling ◽  
Paramagnetic Species ◽  
Magnetic Studies ◽  
Suggested Keywords ◽  
Molecular Cations

Magnetic susceptibility measurements to 4.2 K are reported forO2+[AsF6]−, Br2+[Sb3F16]−, and I2+[Sb2F11]−. The data are interpreted utilizing previous results from photoelectron spectroscopy, known crystal structures, magnetic studies on the superoxide ion and the ozonide ion, and in the case of O2+[AsF6]−, previous ESR studies. The magnetic properties of the three materials are quite different. Br2+[Sb3F16]− obeys Curie–Weiss law between 80 and 4 K: Cm = 0.49 ± 0.01 cm3 mol−1 K and 9 = −0.74 ± 0.01 K (with TIP = 120 × 10−6 cm3 mol−1). The magnetic moment decreases slightly from 2.04 μB at room temperature to 1.93 μB at 4 K. I2+[Sb2F11]− exhibits relatively strong antiferromagnetic coupling with a maximum in χM observed at −54 K. The magnetic moment (corrected for a TIP contribution of 68 × 10−6 cm3 mol−1) decreases from 1.92 μB at 124 K to 0.41 μB at 4 K. Experimental susceptibilities for this compound over the range 300–4 K have been compared to values calculated using three different theoretical models for extended chains of antiferromagnetically coupled paramagnetic species. O2+[AsF6]− exhibits Curie–Weiss behaviour over the range 60–2 K (Cm = 0.34 ± 0.01 cm3 mol−1 K, θ = −1.90 ± 0.01 K). The magnetic moment, uncorrected for TIP, varies from 1.63 μB at 80 K to 1.17 μB at 2 K, and the presence of weak antiferromagnetic coupling in this material is suggested. Keywords: magnetic susceptibilities, dihalogen cations, dioxygenyl cation, low temperature behaviour.

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