341 research outputs found

    Thermal Expansion and Magnetostriction Studies of a Kondo Lattice Compound: Ceagsb2

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    We have investigated a single crystal of CeAgSb2 using low field ac-susceptibility, thermal expansion and magnetostriction measurements in the temperature range 1.5K to 90K. The ac-susceptibility exhibits a sharp peak at 9.7K for both B//c and B perp c due to the magnetic ordering of the Ce moment. The thermal expansion coefficient alpha, exhibits highly anisotropic behaviour between 3K and 80K : alpha is positive for dL/L perp c, but negative for dL/L // c. Furthermore, alpha (for dL/L) perp c (i.e. in ab-plane) exhibits a sharp peak at TN followed by a broad maximum at 20K, while a sharp negative peak at TN followed by a minimum at 20K has been observed for (dL/L //) the c direction. The observed maximum and minimum in alpha(T) at 20K have been attributed to the crystalline field effect on the J=5/2 state of the Ce3+ ion. The magnetostriction also exhibits anisotropic behaviour with a large magnetostriction along the c-axis. The ab-plane magnetostriction exhibits a peak at B=3.3T at 3K, which is consistent with the observed peak in the magnetoresistance measurements.Comment: 4 Pages (B5), 3 figures, submitted to SCES200

    Commensurate to incommensurate magnetic phase transition in Honeycomb-lattice pyrovanadate Mn2V2O7

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    We have synthesized single crystalline sample of Mn2_2V2_2O7_7 using floating zone technique and investigated the ground state using magnetic susceptibility, heat capacity and neutron diffraction. Our magnetic susceptibility and heat capacity reveal two successive magnetic transitions at TN1=T_{N1} = 19 K and TN2=T_{N2} = 11.8 K indicating two distinct magnetically ordered phases. The single crystal neutron diffraction study shows that in the temperature (TT) range 11.8 K ≤T≤\le T \le 19 K the magnetic structure is commensurate with propagation vector k1=(0,0.5,0)k_1 = (0, 0.5, 0), while upon lowering temperature below TN2=T_{N2} = 11.8 K an incommensurate magnetic order emerges with k2=(0.38,0.48,0.5)k_2 = (0.38, 0.48, 0.5) and the magnetic structure can be represented by cycloidal modulation of the Mn spin in ac−ac-plane. We are reporting this commensurate to incommensurate transition for the first time. We discuss the role of the magnetic exchange interactions and spin-orbital coupling on the stability of the observed magnetic phase transitions.Comment: 8 pages, 7 figure

    Unconventional superconductivity in the cage type compound Sc5_5Rh6_6Sn18_{18}

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    We have examined the superconducting ground state properties of the caged type compound Sc5_5Rh6_6Sn18_{18} using magnetization, heat capacity, and muon-spin relaxation or rotation (μ\muSR) measurements. Magnetization measurements indicate type-II superconductivity with an upper critical field μ0Hc2(0)\mu_0H_{c2}(0) = 7.24 T. The zero-field cooled and field cooled susceptibility measurements unveil an onset of diamagnetic signal below TcT_{\bf c} = 4.4 K. The interpretation of the heat capacity results below TcT_{\bf c} using the α−\alpha-BCS model unveils the value of α\alpha = 2.65, which gives the dimensionless ratio 2Δ(0)/kBTc\Delta(0)/k_B T_{\bf c} = 5.3, intimating that Sc5_5Rh6_6Sn18_{18} is a strong-coupling BCS superconductor. The zero-field μ\muSR measurements in the longitudinal geometry exhibit a signature of a spontaneous appearance of the internal magnetic field below the superconducting transition temperature, indicating that the superconducting state is characterized by the broken time-reversal symmetry (TRS). We have compared the results of broken TRS in Sc5_5Rh6_6Sn18_{18} with that observed in R5_5Rh6_6Sn18_{18} (R = Lu and Y).Comment: 6 pages, 4 figures. arXiv admin note: text overlap with arXiv:1411.687

    Magnetic and transport properties of Pr2Pt3Si5

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    We have investigated the magnetic and transport properties of a polycrystalline Pr2Pt3Si5 sample through the dc and ac magnetic susceptibilities, electrical resistivity, and specific heat measurements. The Rietveld refinement of the powder X-ray diffraction data reveals that Pr2Pt3Si5 crystallizes in the U2Co3Si5-type orthorhombic structure (space group Ibam). Both the dc and ac magnetic susceptibility data measured at low fields exhibit sharp anomaly near 15 K. In contrast, the specific heat data exhibit only a broad anomaly implying no long range magnetic order down to 2 K. The broad Schottky-type anomaly in low temperature specific heat data is interpreted in terms of crystal electric field (CEF) effect, and a CEF-split singlet ground state is inferred. The absence of the long range order is attributed to the presence of nonmagnetic singlet ground state of the Pr3+ ion. The electrical resistivity data exhibit metallic behavior and are well described by the Bloch-Gr\"uniesen-Mott relation.Comment: 6 pages, 8 figure
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