Exchange bias with Fe substitution in LaMnO3

Abstract

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

Exchange bias effect in alloys and compounds

“…First report of EB effect as a result of Mn-site substitution was found in LaMn 0.7 Fe 0.3 O 3 [180]. It was noticed that EB effect was observed only at 30 % of Fe substitution which was absent for other compositions with different percentage of Fe content.…”

“…The effect of Mn-site substitution and EB effect have been investigated in La 1−y Mn 1−x Fe x O 3 [180,181,182] and Bi 0.4 Ca 0.6 Mn 1−x Ti x O 3 [183]. First report of EB effect as a result of Mn-site substitution was found in LaMn 0.7 Fe 0.3 O 3 [180].…”

The exchange bias effect in phase separated Nd1−xSrxCoO3at the spontaneous ferromagnetic/ferrimagnetic interface

“…[6] Recently, the signature of EB effect has been reported at the spontaneous interfaces for few mixed-valent manganites and cobaltites with perovskite structure. [7,8,9,15,23,24] The first report was found in a charge ordered (CO) compound Pr 1/3 Ca 2/3 MnO 3 , where ferromagnetic (FM) droplets were spontaneously embedded in an antiferromagnetic (AFM) background creating the FM/AFM interface. [7] The EB phenomenon has also been reported for another * Electronic address: sspsg2@iacs.res.in CO manganite Y 0.2 Ca 0.8 MnO 3 , where a strong cooling field dependence of EB is observed due to a considerable change of phase fraction between FM/AFM layers.…”

“…[7] The EB phenomenon has also been reported for another * Electronic address: sspsg2@iacs.res.in CO manganite Y 0.2 Ca 0.8 MnO 3 , where a strong cooling field dependence of EB is observed due to a considerable change of phase fraction between FM/AFM layers. [8] Recently, we observed the signature of EB phenomenon in the cluster-glass (CG) compounds LaMn 0.7 Fe 0.3 O 3 and La 0.87 Mn 0.7 Fe 0.3 O 3 , [9,10] where short range FM clusters are embedded in a SG-like matrix creating spontaneous FM/SG interface. [9,11,12,13] The average size of the FM clusters is found to decrease systematically with decreasing particle size, which has a strong influence on the EB phenomenon.…”

Reentrant-spin-glass state inNi2Mn1.36Sn0.64shape-memory alloy

“…The origin of EB is gener- * Electronic address: sspsm2@iacs.res.in ally ascribed to the presence of FM and AFM interfacial coupling in a heterogeneous sample. EB has also been observed in materials having FM/spin-glass (SG) and FM/Ferrimagnet interfaces [14,15] other than FM/AFM systems. However in all the cases, it is required that the ordering temperature (T N F ) for the non-ferromagnetic phase (may be AFM, SG or ferrimagnet) should be lower than the ferromagnetic Curie point (T C ).…”