Giant radio-frequency magnetoabsorption effect in the cobaltite ceramic La0.5Sr0.5CoO3

Abstract

The DC transport properties of and the radio-frequency (RF) wave absorption (at 1.33 MHz) in a ceramic sample of La0.5Sr0.5CoO 3−δ are measured. The Curie temperature, Tc, of the sample is about 250 K. A giant negative magnetoabsorption effect is found. In the vicinity of Tc, the absolute value of the magnetoabsorption is about 38% in the rather low magnetic field 2.1 kOe. This differs drastically from the measured DC magnetoresistance (MR) δ(H) = [R(0) − R(H)]/R(0) which is a mere 0.26 % near Tc in the same field and increases to about 2.15 % in H = 20 kOe. The phenomenon can be understood taking into account that the magnetoabsorption is determined by influence of magnetic field on the conductivity and the magnetic permeability, while the MR is determined solely by the former. The magnetoabsorption effect can be used to develop RF devices controlled by magnetic field and temperature.

Study of the temperature dependence of magnetic permeability, selectivity and D.C. resistivity of LaKMnMoO 6

“…Finally, it is important to mention that the permeability exhibits a peak at the Curie temperature T c as expected [10], this finding enhances the accuracy of T c determination in both the present work and the previously reported work [1], since it was determined by two independent and quite separate experiments. A similar increase in the permeability at T C was reported by Belevtsev et al [5] Fig. 3 shows the evolution of the selectivity versus temperature for a chosen frequency (1.6 MHz), it can be seen that the selectivity has at first a nearly constant value then it decreases upon cooling around T C then it has a constant value again below 160 K. This can be interpreted by considering the definition of the selectivity; since it is the reciprocal of the quality factor Q: S = 1/Q = R/X L ; where X L is the component inductance, R is not only the ohmic resistance of the coil but also including what is called the reflected resistance in the coil due to losses in the core.…”

Giant magnetic-field changes in radio-frequency absorption in La0.67Sr0.33MnO3 near the Curie temperature

“…For this reason, the optimal frequency for observation of giant changes in high-frequency absorption should be of the order of 1 MHz, that is, in the radio-frequency (RF) range. For example, a giant RF magnetoabsorption is found in cobaltite La 0.5 Sr 0.5 CoO 3 [7] which is a FM perovskite-like oxide related to manganites but with a far smaller MR. The relative change in magnetoabsorption in this compound was found to be about 38 % near the Curie temperature (about 250 K) in a rather weak magnetic field 2.1 kOe at frequency 1.33 MHz [7].…”

“…For example, a giant RF magnetoabsorption is found in cobaltite La 0.5 Sr 0.5 CoO 3 [7] which is a FM perovskite-like oxide related to manganites but with a far smaller MR. The relative change in magnetoabsorption in this compound was found to be about 38 % near the Curie temperature (about 250 K) in a rather weak magnetic field 2.1 kOe at frequency 1.33 MHz [7].…”

Correlation between magnetoimpedance and permeability in La2/3Ba1/3MnO3

“…In addition to CMR/LFMR effect, perovskite manganites exhibit giant magnetoabsorption in the microwave high frequencies [10][11][12][13] and giant magnetoimpedance (GMI) in radio frequencies . A giant radio-frequency magnetoabsorption effect was also observed in cobaltite La 0.5 Sr 0.5 CoO 3 [35], which is a ferromagnetic perovskite oxide but has far smaller dc magnetoresistance than the manganites. The relative change in magnetoabsorption for this La-Sr cobaltite was found to be about -38% near the Curie temperature (about 250 K) in a low magnetic field 2.1 kOe at the frequency of 1.33 MHz [35].…”

“…A giant radio-frequency magnetoabsorption effect was also observed in cobaltite La 0.5 Sr 0.5 CoO 3 [35], which is a ferromagnetic perovskite oxide but has far smaller dc magnetoresistance than the manganites. The relative change in magnetoabsorption for this La-Sr cobaltite was found to be about -38% near the Curie temperature (about 250 K) in a low magnetic field 2.1 kOe at the frequency of 1.33 MHz [35]. Giant magnetoimpedance effects have also been found in soft magnetic metallic materials, such as amorphous Co-Fe-Si-B and Fe-based nanocrystalline wires and ribbons [36][37][38][39][40].…”