2 research outputs found

    Evidences for magnetic dimers and skyrmion lattice formation in Eu2_2Pd2_2Sn

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    Magnetic, thermal and transport properties of the non-centrosymmetric compound Eu2_2Pd2_2Sn are revisited after including new measurements. In its paramagnetic phase, the outstanding feature of this compound is the formation of Eu2+^{2+} dimers that allows to understand the deviation of the magnetic susceptibility χ(T)\chi(T) from the C-W law below about 70\,K, the field dependent magnetization M(B)M(B) variation below 80\approx 80\,K and the reduced entropy at the ordering temperature S(TN)=0.64Rln(8)S(T_N)= 0.64R\ln(8). A significant change of the exchange interactions occurs between T70T\approx 70\,K (where θP=18\theta_P = 18\,K) and TN=13.3T_N = 13.3\,K (where θP=4.5\theta_P =-4.5\,K). The strong electronic overlap, arising from the reduced Eu-Eu spacing compared with that of pure Eu2+^{2+} is expected to power these quasiparticles formation, inducing a significant reformulation of the magnetic structure. A rich magnetic phase diagram is obtained from the analysis of the derivatives of the magnetic parameters: χ/T\partial \chi/\partial T and M/B\partial M/\partial B, and the field dependence of the specific heat. Two critical points are recognized and a tentative description of the magnetic structures is proposed. The possible formation of a skyrmion lattice, that arises from the presence of magnetically frustrated pockets in the phase diagram, is suggested by theoretical studies on hexagonal structures exhibiting similar interactions pattern.Comment: 13 pages, 11 figure

    Ring diagrams and electroweak phase transition in a magnetic field

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    Electroweak phase transition in a magnetic field is investigated within the one-loop and ring diagram contributions to the effective potential in the minimal Standard Model. All fundamental fermions and bosons are included with their actual values of masses and the Higgs boson mass is considered in the range 75GeVmH115GeV75 GeV \leq m_H \leq 115 GeV. The effective potential is real at sufficiently high temperature. The important role of fermions and WW-bosons in symmetry behaviour is observed. It is found that the phase transition for the field strengths 1023102410^{23} - 10^{24}G is of first order but the baryogenesis condition is not satisfied. The comparison with the hypermagnetic field case is done.Comment: 16 pages, Latex, changed for a mistake in the numerical par
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