Influence of magnetic field on the paramagnetic-ferromagnetic transition in aLa1−xCaxMnO3

Abstract

The ultrasonic properties of La1−xCaxMnO3 (x ≈ 0.25) with the Curie temperature TC about 200 K are studied. Temperature dependences of longitudinal and transverse sound velocities were measured in zero magnetic field and for different constant magnetic fields as well. The ultrasonic study is supported by magnetic, resistive, magnetoresistive, structural and other measurements of the sample that facilitate interpretation of the results obtained. The magnetic field influence on sound properties found in this study presents some new features of the interplay between the elastic and magnetic properties of these compounds. It is shown that the paramagnetic-ferromagnetic transition in the sample studied is first order, but can become second order under the influence of applied magnetic field.

Study of the conductivity behavior of La0.75Ca0.25MnO3 in the vicinity of the ferromagnetic-paramagnetic transition with the use of single current pulses

“…At those parameters, the oscillograms of the first type were realized ( Fig.1) which was indicative of the fulfillment of the Ohm law. The obtained relation R 0 (T ) coincides with the temperature dependence R(T ), measured on the same specimen [6] at low DC current below 5 mA. Fig.2 shows the relations R J (T ) for three current values of 2.7, 5.4 and 8 A, which were realized accordingly in 0.25, 0.5 and 0.75 ms after triggering the pulse.…”

“…The present study concerns with the non-linear effect in conductivity of a bulk specimen of La 0.75 Ca 0.25 MnO 3 grown by the floating-zone technique with the radiation heating [6,7]. The sample structure was close to being single-crystal.…”

“…The specimen studied in this research had been investigated in reference [6] where DC resistance, magnetization, velocity and absorption of the sound were measured. The anomalies of these properties observed in reference [6] in the vicinity of the PM-FM transition were interpreted in terms of the existence of a multi-phase state near T C .…”

Griffiths phase and critical behavior in single-crystalLa0.7Ba0.3MnO3: Phase diagram forJiang1, Zhou2, Williams3 et al. 2008Phys. Rev. B

“…17͒ and with recent data on the Ca-doped system near the ferromagnetic metal-ferromagnetic insulator ͑FM-FI͒ boundary. 4 Indeed, an inspection of the various structurally based parameters 3,4,11,13,[17][18][19][20][21][22][23][24]27,28 for these systems reproduced in Table I reveals that not a single such parameter reflects the detailed variations in these temperatures, the exponent , and the accompanying field dependence of GP behavior, outlined above, away from optimal doping.…”

Synthesis and on-line ultrasonic characterisation of bulk and nanocrystalline La0.68Sr0.32MnO3 perovskite manganite

“…Over the past few years, perovskite manganites R 1−x A x MnO 3 (where R trivalent rare earth elements and A divalent alkaline earth ions) were attracted for potential applications like solid oxide fuel cells, magnetic sensors/reading heads and frequency switching devices due to their unique physico-chemical [1][2][3], and giant magneto resistance (GMR) properties [4][5][6][7][8]. In perovskite magnetic materials, particularly La 0.68 Sr 0.32 MnO 3 (LSMO) perovskite, the existence of highest value of Curie temperature (T C ) and very low carrier density with a high spin polarisation of charge carriers make them very promising candidate for room temperature applications.…”