Unusual field dependence of radio frequency magnetoimpedance in La_0.67Ba_0.33MnO₃

Abstract

Magnetic-field dependence of the ac impedance Z(f,H)=R(f,H)+jX(f, H) in La0.67Ba0.33MnO3 carried out over a wide frequency range (f=0 to 30 MHz) reveals a huge low-field ac magnetoresistance, ΔR/R=-55% at f=15 MHz and magnetoreactance, ΔX/X=-80% at f=3 MHz in μ0H=100 mT at room temperature. We show contrasting evolution of ΔR/R and ΔX/X with increasing magnetic field and frequency. While ΔR/R is negative and shows a single peak at μ0H=0 T for all but f=30 MHz, the single peak in ΔX/X transforms into a valley at the origin and a double peak at H=±Hk which shifts upward in H with increasing frequency. The ΔX/X eventually changes sign from negative to positive above 25 MHz. The observed features in ΔX/X suggest possible occurrence of ferromagnetic resonance in MHz range.

Low temperature resistivity anomalies in bismuth doped manganites

“…According to the theory of Lee and Ramakrishnan [9], as the electron-electron interaction varies as T 1/2 , e T 1/2 was introduced in Eq. (2). The experimental resistivity data of present investigation were fitted to Eq.…”

“…In general, these properties are derived from a close interplay of lattice, charge and spin degrees of freedom. Further, extensive efforts are underway in different laboratories to enhance the magnitude of magnetoresistance at low fields, particularly in milli and micro Tesla range using techniques such as artificial grain boundaries and tunnel junctions [1,2]. Although a lot of work on Re 0.67 A 0.33 MnO 3 [where Re is La, Nd, Pr, etc., and A is Ca, Sr, Ba, etc.,] manganites has been published [3][4][5], the physical origin behind the conduction mechanism and its correlation with magnetoresistance, especially at low temperatures is still elusive.…”

Low temperature resistivity minimum and its correlation with magnetoresistance in La0.67Ba0.33MnO3 nanomanganites

“…It is well known that the coupling between the localized spin and conduction electrons, serves as a fundamental model for understanding Physics of correlated electrons. As a consequence, the interplay between electronic and magnetic degrees of freedom has been intensively studied in manganites for the past two decades [3][4][5][6][7].…”

Alternating current magnetotransport in Sm0.1La0.6Sr0.3MnO3

“…However, four-probe ac electrical response of ferromagnetic metallic manganites in the lower end of radio frequency spectrum (f = 1 kHz to 20 MHz) has been seldom reported. A few available reports 9,10 suggest that the magnitude of the magnetoresistance in sub-kilogauss magnetic fields is greatly enhanced with ac current excitation, but the mechanism of ac magnetoresistance as well as factors affecting the ac magnetoresistance are not clearly understood yet.…”