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The exchange bias (EB) in LaMn0.7Fe0.3O3 is observed by the negative shift and training effect of the hysteresis loops, while the sample was cooled in external magnetic field. The analysis of cooling field dependence of EB gives the size of the ferromagnetic (FM) cluster ≈ 25 Å, where the magnetic anisotropy of FM cluster is found two order of magnitude higher than the FM bulk manganites. We propose that the nanoscale FM clusters are embedded in the glassy magnetic host with EB at the FM/glassy magnetic interface.Introduction. -Recently, the observation of exchange bias (EB) in the phase separated (PS) charge ordered (CO) manganites opens up a new prospective of technological applications in addition to the colossal magnetoresistance (CMR) properties. [1, 2] Exchange bias is a novel phenomenon, which is ascribed to the induced exchange anisotropy at the interface between ferromagnetic (FM) and antiferromagnetic (AFM) phases in a heterogeneous system. [3,4] The induced exchange anisotropy is unidirectional in character and increases the effective anisotropy of the heterogeneous system, which has the technological applications for storage and spin-electron devices. The evidence of EB was first discovered by Meiklejohn and Bean in 1956 for FM Co core and AFM CoO shell structure, [5] which has also been observed at the FM/spin-glass (SG) interface. [6][7][8][9] In addition to the technological importance, the evidence of EB further provides the microscopic views of the inhomogeneous phase separation in manganites. The first evidence of EB was observed in CO manganite Pr 1/3 Ca 2/3 MnO 3 , where ferromagnetic (FM) droplets are naturally embedded in the AFM background. [1] The other example of EB have recently been reported for CO manganite, where the strong cooling field dependence of EB is ascribed to the thickness of the FM layer in a spontaneous lamellar ferromagnetic/antiferromagnetic phase separated Y 0.2 Ca 0.8 MnO 3 . [2] In this letter, we also report the EB for 30 % Fe substitution in LaMnO 3 at the FM/glassy magnetic interface. Notably, we observe the EB at the FM/glassy magnetic interface in contrast to the phenomanon at the FM/AFM interface for CO manganites. The EB was characterised by the unidirectional shift of the magnetic hysteresis loops under different field-cooled conditions, which was further confirmed by the training effect.Experimental procedure. -The polycrystalline sample of LaMn 0.7 Fe 0.3 O 3 was prepared by a chemical route. [10] The single rhombohedral phase (R3c) of the compound

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The cluster-glass compound LaMn 0.7 Fe 0.3 O 3 was synthesized with average particle sizes ∼20, ∼90, and ∼300 nm. We observed a shift of the magnetic hysteresis loop in the field axis while the sample was cooled in an external magnetic field. The systematic shift of the hysteresis loops and the cooling field dependence of the shift indicated the phenomenon of exchange bias. The exchange bias field was found to be strongly dependent on the particle size, where the exchange bias field decreased considerably with an increase of particle size, and the weak effect of exchange bias was observed for particles with size ∼300 nm. A cluster-glass state with short range ferromagnetic clusters embedded in the spin-glass like host has been proposed, where the average size of the ferromagnetic cluster increases with particle size.