Anomalous lattice expansion of RuSr2Eu1.5Ce0.5Cu2O10(Ru-1222) magneto superconductor: A low temperature X-ray diffraction study

This is the first report of the observation of the onset of excess volume and also of the strain along the a-axis near the magnetic ordering temperature in Ru-1222 superconductor, and indicates a coupling between the lattice and the magnetism in this system. Magnetization, magneto transport and thermoelectric power measurements being carried out on the same sample are also reported.Comment: 15 Pages Text Plus Figs. Physica C (2006) accepte

Scaling of the isothermal entropy change and magnetoresistance in Ni-Mn-In based off-stoichiometric Heusler alloys

We show that for identical changes in magnetic field, the temperature dependence of the change in isothermal entropy across the martensite-austenite phase transition in different Ni-Mn-In based off-stoichiometric Heusler alloys scales to a single curve. The temperature dependence of magnetoresistance across the same martensite-austenite phase transition in these alloys also scales to follow a similar curve. The temperatures corresponding to the peak value of the isothermal entropy change and the peak magnetoresistance for a particular applied magnetic field are correlated with distinct features observed in the magnetization vs. temperature and resistivity vs. temperature curves respectively of these alloys (in the same magnetic field). These findings can be utilized in estimating the useful temperature regime for the isothermal entropy change and magnetoresistance of Ni-Mn-In based alloys with newer compositions, and to predict the magnitude of these functionalities, without performing actual experiments

The influence of electron-phonon coupling and spin fluctuations on the superconductivity of the Ti-V alloys

We report a study of the normal and superconducting state properties of the TixV1−x alloys for x = 0.4, 0.6, 0.7 and 0.8 with the help of dc magnetization, electrical resistivity and heat capacity measurements along with the electronic structure calculation. The superconducting transition temperature Tc of these alloys is higher than that of elemental Ti and is also higher than elemental V for x ≤ 0.7. The roles of electron density of states, electron-phonon coupling and spin fluctuations in the normal and superconducting state properties of these alloys have been investigated in detail. The experimentally observed value of Tc is found to be considerably lower than that estimated on the basis of electron density of states and electron-phonon coupling in the x = 0.4, 0.6 and 0.7 alloys. There is some evidence as well for the preformed Cooper pair in all these Ti-V alloys in the temperature regime well above Tc. Similar to x = 0.6 [Md. Matin, L.S. Sharath Chandra, R.K. Meena, M.K. Chattopadhyay, A.K. Sinha, M.N. Singh, S.B. Roy, Physica B 436, 20 (2014)], the normal state properties of the x = 0.4 alloy showed the signature of the presence of spin fluctuations. The difference between the experimentally observed Tc and that estimated by considering electron density of states and electron-phonon coupling in the x = 0.4, 0.6 and 0.7 alloys is attributed to the possible influence of these spin fluctuations. We show that the non-monotonous variation of Tc as a function of x in the TixV1−x alloys is due to the combined effects of the electron-phonon coupling and the spin fluctuations