Barkhausen-like steps and magnetic frustration in doped La0.67-xAxCa0.33MnO3 (A: Ce,Y)

G. ALEJANDRO, L.B. STEREN, A. CANEIRO, J. CARTES, E.E. VOGEL, P. VARGAS.

PHYSICAL REVIEW B - CONDENSED MATTER AND MATERIALS PHYSICS

American Physical Society

Lugar: New York; Año: 2006 vol. 73 p. 54427 - 54433

0163-1829

We present dc magnetization experiments performed on the doped,polycrystalline system La$_{0.67-x}$A$_x$Ca$_{0.33}$MnO$_{3}$ (A:Ce,Y). The ceramic samples have been obtained by the nitratedecomposition route and structurally characterized by powder X-raydiffraction. Hysteresis loops reveal an exciting and non repetitivemulti-step structure of Barkhausen-like jumps in the low fieldsregion, up to 50 Oe. We discuss our results in terms of a collectiveresponse of magnetic moments pinned by frustration due to thecompetition among different exchange interactions present in thecompounds. A simple Ising Hamiltonian with in-plane ferromagneticinteractions and randomly mixed off-plane interactions is introducedto model this hypothesis. Computer simulations based on this modelallow us to reproduce most of the features observed in thehysteresis curves, allowing a qualitative understanding of thecomplex magnetic behavior of this family of manganites.