Thermal diffusivity of La1-x Sx MnO3 (x < 0.3)
International Journal of Thermophysics 25:4 (2004) 1269-1279
Abstract:
Perovskite manganites are interesting because of their colossal magnetoresistance. In this work high resolution thermal diffusivity measurements of La1-xSrxMnO3 (0 ≤ x ≤ 0.3) single crystals in the temperature range from 250 to 400 K are presented. A photopyroelectric device in the standard back configuration has been used. The thermal diffusivity through second-order magnetic phase transitions, as well as through first- and second-order structural phase transitions has been measured. The critical parameters of the sample with x = 0.3 at the ferromagnetic-to- paramagnetic transition have been obtained, and are close to the values predicted by the Ising model.Critical behavior dependence on Sr concentration in La1-xSrxMnO3
J APPL PHYS 95:11 (2004) 7366-7368
Abstract:
The thermal diffusivity in the vicinity of the magnetic transition of a set of La1-xSrxMnO3 (0less than or equal toxless than or equal to0.3) single crystals has been measured using the photopyroelectric technique. Taking into account that the inverse of the thermal diffusivity behaves as the specific heat, the critical exponent alpha has been obtained. In the pure and lightly doped samples (x=0,0.05) where the transition is antiferromagnetic-paramagnetic, the critical exponent is consistent with the Heisenberg model (alpha=-0.115). For Sr concentration higher than 0.20, where the low temperature phase is ferromagnetic, a drastic change in the critical exponent has been observed, approaching Ising behavior (alpha=+0.11) at the highest concentration. (C) 2004 American Institute of Physics.Ferromagnetic in-plane spin fluctuations in NaxCoO2 observed by neutron inelastic scattering
Physical Review Letters 92 (2004) article 197201 4pp
Magnetization of charge-ordered La2-xSrxNiO4+delta
J MAGN MAGN MATER 272 (2004) 958-959
Abstract:
We report magnetization measurements on La2-xSrxNiO4+delta single crystals, with 0less than or equal toxless than or equal to0.5. Glassy behaviour associated with the formation of spin-charge stripes, and a separate spin-glass phase at low temperatures were observed. We have also found a 'memory effect' in the magnetic field-temperature history, which is found to be suppressed in the low-temperature spin state of the x = 0.333 crystal. (C) 2003 Elsevier B.V. All rights reserved.Spin excitations in stripe-ordered La2-xSrxNiO4 (x=0.275 and 1/3)
J MAGN MAGN MATER 272-76 (2004) 265-266