Magneto-impedance Measurements In Bulk Samples Of La0.7ca 0.3mno3 And La0.6y0.1ca 0.3mno3

In this work, magneto-resistance and magneto-impedance (MI) data for bulk samples of pure and Y-doped La0.7Ca0.3MnO3 manganites are reported. Temperature dependent measurements were carried out sweeping the applied magnetic field H in the -6T<H<6T range. The measurements were done with dc and ac electrical currents, varying the frequencies f up to 5MHz, using a four-probe technique. The pure La 0.7Ca0.3MnO3 sample presented a metal-insulator-transition near the ferromagnetic transition (TC = 245K). For these samples, magneto-resistance of the order 60% for H = 6T was observed close to TC. The substitution of ions of La by Y (La 0.6Y0.1Ca0.3MnO3) reduced T C to 170K but, on the other hand, increased the magneto-resistance to over 90% near TC. In the measurements with ac currents, the data for both samples presented a large magneto-impedance effect. The MI is more pronounced at high fields and for the Y-doped samples. Moreover, the Y-doped samples showed a strong hysteretic behavior that was not observed in the pure samples. © 2003 Elsevier B.V. All rights reserved.3691-2108111Volger, J., (1954) Physica, 20, p. 49Von Helmolt, R., Wecker, J., Holzapfel, B., Schultz, L., Samwer, K., (1993) Phys. Rev. Lett., 71, p. 2331Zener, C., (1951) Phys. Rev., 82, p. 403Machado, F.L.A., Da Silva, B.L., Rezende, S.M., Martins, C.S., (1994) J. Appl. Phys., 75, p. 6563Machado, F.L.A., Rezende, S.M., (1996) J. Appl. Phys., 79, p. 6558Hu, J., Qin, H., (2001) J. Magn. Magn. Mater., 231, p. 1Srinivasu, V.V., Lofland, S.E., Bhagat, S.M., (1999) J. Appl. Phys., 86, p. 1067Qin, H., Hu, J., Chen, J., (2002) J. Appl. Phys., 91, p. 10003Fonseca, F.C., Souza, J.A., Jardim, R.F., Muccillo, R., Muccillo, E.N.S., Gouvêa, D., Jung, M.H., Lacerda, A.H., (2003) Phys. Status Solids (a), 199, p. 255Freitas, R.S., Ghivelder, L., Damay, F., Dias, F., Cohen, L.F., (2001) Phys. Rev. B, 64, p. 14440