Magneto-transport and exchange biasing in La-Ca-Mn-O compositionally modulated ferromagnetic/antiferromagnetic multilayers

Compositionally modulated structures consisting of La2/3Ca1/3MnO3 ferromagn etic (FM) layers and La1/3Ca2/3MnO3 antiferromagnetic (AF) layers, with lay er thickness 1.5 nm less than or equal to t(FM),t(AF)less than or equal to 6 nm, were grown on (100)LaAlO3 by pulsed laser deposition. Thermomagnetic and isothermal magnetic measurements reveal an exchange-biasing mechanism w ith the same blocking temperature T(B)approximate to 70 K for all the exami ned combinations of t(FM) and t(AF). The ratio of colossal magnetoresistanc e increases in multilayers with larger t(FM), whereas the exchange-biasing field increases in samples with larger t(AF). The independence of T-B on t( FM) and t(AF) shows that the artificially induced La1-xCaxMnO3 (x approxima te to 0.5) compositional modulation at the interfaces is of critical import ance for exchange biasing in La-Ca-Mn-O based multilayers. (C) 2000 America n Institute of Physics. [S0021-8979(00)01708-4].