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Giant ac electrical response of La0.7Sr0.3MnO3 in sub-kilogauss magnetic fields

Published online by Cambridge University Press:  01 February 2011

Alwyn Rebello ,
Vinayak Bharat Naik ,
Sujit Kumar Barik ,
Mark Choong Lam  and
Mahendiran Ramanathan
Alwyn Rebello
Affiliation:
alwyn@nus.edu.sg, National University of Singapore, Department of Physics, Singapore, Singapore
Vinayak Bharat Naik
Affiliation:
naik@nus.edu.sg, Natioanl University of Singapore, Department of Physics, Singapore, Singapore
Sujit Kumar Barik
Affiliation:
skbarik@nus.edu.sg, National University of Singapore, Department of Physics, Singapore, Singapore
Mark Choong Lam
Affiliation:
g0806648@nus.edu.sg, National University of Singapore, Department of Physics, Singapore, Singapore
Mahendiran Ramanathan
Affiliation:
phyrm@nus.edu.sg
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Abstract

We report ac electrical transport in the metallic ferromagnet La0.7Sr0.3MnO3. Both ac resistance (R) and reactance (X) were measured as a function of temperature (T= 400-100 K), frequency of the ac current (f = 100 kHz – 20 MHZ) and external dc magnetic field (H = 0-100 mT) applied parallel to the current direction. It is shown that, while R(H = 0 T) decreases smoothly around the Curie temperature (TC) for f = 100 kHz, an abrupt increase followed by a peak close to TC occurs for f ≥ 500 kHz. The peak decreases in magnitude, broadens and shifts down in temperature with increasing values of H. The peak in R is completely suppressed under H= 100 mT resulting in a huge low-field ac magnetoresistance (R/R= -53 % for f= 2MHz) whereas the dc magnetoresistance only -31 % even at H = 7 T. While the reactance X(H = 0 T) also shows an abrupt increase at TC for f < 10 MHz, it decreases abruptly at TC for f ≥ 12 MHz. The magnetoreactance is largest (X/X= -47 %) at f = 100 kHz and it changes sign from negative to positive with increasing frequency. It is suggested that the observed huge ac magnetoresistance arises from decrease of magnetic permeability which enhances skin depth under a magnetic field. Our results indicate that the extraordinary sensitivity of the ac magnetoresistance to low dc magnetic fields can be exploited for device applications.

Keywords

magnetoresistance (transport)magnetoresistance (magnetic)magnetic properties
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1256: Symposium N – Functional Oxide Nanostructures and Heterostructures , 2010 , 1256-N04-01
Copyright
Copyright © Materials Research Society 2010

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