Magnetocaloric effect in the spin-1/2 Ising-Heisenberg diamond chain with the four-spin interaction

The magnetocaloric effect in the symmetric spin-1/2 Ising–Heisenberg diamond chain with the Ising four-spin interaction is investigated using the generalized decoration-iteration mapping transformation and the transfer-matrix technique. The entropy and the Grüneisen parameter, which closely relate to the magnetocaloric effect, are exactly calculated to compare an ability of the system to cool in the vicinity of different field-induced ground-state phase transitions during the adiabatic demagnetization.Дослiджено магнетокалоричний ефект у симетричному ромбiчноподiбному ланцюжку Iзiнга-Гайзенберга iз чотириспiновою взаємодiєю Iзiнга, використовуючи узагальнене декорацiйно-iтерацiйне перетворення i метод трансфер-матрицi. Ентропiя i параметр Грюнайзена, який тiсно пов’язаний з магнетокалоричним ефектом, обчислено точно для того, щоб порiвняти здатнiсть системи холонути в околi рiзних фазових переходiв, iндукованих полем, пiд час адiабатичного розмагнiчення

Inverse magnetocaloric effect in spin-1/2 Fisher's super-exchange antiferromagnet

The isothermal entropy change and the adiabatic temperature change are rigorously calculated for the exactly solved spin-1/2 Fisher's super-exchange antiferromagnet in order to examine magnetocaloric properties of the model in a vicinity of the second-order phase transition. It is shown that the large inverse magnetocaloric effect occurs around the temperature interval T_c(h≠0) < T < T_c(h=0) for any magnetic-field change Δh:0 → h. The most pronounced inverse magnetocaloric effect can be found for the magnetic-field change, which coincides with the critical field of a zero-temperature phase transition from the antiferromagnetically ordered ground state to the paramagnetic one

The Hilbert Space and the Exact Solution of the Spin-Electron Double-Tetrahedral Chain

We discuss an exactly solvable double-tetrahedral chain, in which the localized Ising spins regularly alternate with triangular clusters - each available for one mobile electron. We give an exact solution for the considered hybrid system by the construction of the N-th tensor power of the Fourier transformation and using the generalized decoration-iteration mapping tranformation

The Hilbert Space and the Exact Solution of the Spin-Electron Double-Tetrahedral Chain

We discuss an exactly solvable double-tetrahedral chain, in which the localized Ising spins regularly alternate with triangular clusters - each available for one mobile electron. We give an exact solution for the considered hybrid system by the construction of the N-th tensor power of the Fourier transformation and using the generalized decoration-iteration mapping tranformation

Ground-State Properties of the Spin-1/2 Heisenberg-Ising Bond Alternating Chain with Dzyaloshinskii-Moriya Interaction

Ground-state energy is exactly calculated for the spin-1/2 Heisenberg-Ising bond alternating chain with the Dzyaloshinskii-Moriya interaction. Under certain condition, which relates a strength of the Ising, Heisenberg and Dzyaloshinskii-Moriya interactions, the ground-state energy exhibits an interesting nonanalytic behavior accompanied with a gapless excitation spectrum

Using ferromagnetic nanoparticles with low Curie temperature for magnetic resonance imaging-guided thermoablation

V&iacute;t Herynek,1 Karol&iacute;na Turnovcov&aacute;,2 Pavel Veverka,3 Tereza Dědourkov&aacute;,4,5 Pavel Žv&aacute;tora,6 Pavla Jendelov&aacute;,2 Andrea G&aacute;lisov&aacute;,1 Lucie Kosinov&aacute;,7 Kl&aacute;ra Jir&aacute;kov&aacute;,2 Eva Sykov&aacute;2 1MR-Unit, Radiodiagnostic and Interventional Radiology Department, Institute for Clinical and Experimental Medicine, Prague, 2Department of Neuroscience, Institute of Experimental Medicine, 3Department of Magnetics and Superconductors, Institute of Physics, Czech Academy of Sciences, Prague, 4Department of Inorganic Technology, Faculty of Chemical Technology, University of Pardubice, 5SYNPO, akciov&aacute; společnost, Pardubice, 6Department of Analytical Chemistry, Institute of Chemical Technology, 7Diabetes Center, Institute for Clinical and Experimental Medicine, Prague, Czech&nbsp;Republic Introduction: Magnetic nanoparticles (NPs) represent a tool for use in magnetic resonance imaging (MRI)-guided thermoablation of tumors using an external high-frequency (HF) magnetic field. To avoid local overheating, perovskite NPs with a lower Curie temperature (Tc) were proposed for use in thermotherapy. However, deposited power decreases when approaching the Curie temperature and consequently may not be sufficient for effective ablation. The goal of the study was to test this hypothesis. Methods: Perovskite NPs (Tc =66&deg;C&ndash;74&deg;C) were characterized and tested both in vitro and in&nbsp;vivo. In vitro, the cells suspended with NPs were exposed to a HF magnetic field together with control samples. In vivo, a NP suspension was injected into a induced tumor in rats. Distribution was checked by MRI and the rats were exposed to a HF field together with control animals. Apoptosis in the tissue was evaluated. Results and discussion: In vitro, the high concentration of suspended NPs caused an increase of the temperature in the cell sample, leading to cell death. In vivo, MRI confirmed distribution of the NPs in the tumor. The temperature in the tumor with injected NPs did not increase substantially in comparison with animals without particles during HF exposure. We proved that the deposited power from the NPs is too small and that thermoregulation of the animal is sufficient to conduct the heat away. Histology did not detect substantially higher apoptosis in NP-treated animals after ablation. Conclusion: Magnetic particles with low Tc can be tracked in vivo by MRI and heated by a HF field. The particles are capable of inducing cell apoptosis in suspensions in vitro at high concentrations only. However, their effect in the case of extracellular deposition in vivo is questionable due to low deposited power and active thermoregulation of the tissue. Keywords: perovskite nanoparticles, hyperthermia, high-frequency magnetic field, MRI, tumor ablatio