Chemical pressure induced substantial negative exchange bias on zero field cooled nanocrystalline LaFeO3

Abstract

We report a distinctly different zero feld cooled negative exchange bias(EB) effect in Ni doped LaFeO _3 nanoparticle where the EB field is both temperature and concentration dependent. Nanoparticles of Ni substituted LaFeO _3 is prepared by a sol-gel process. The broadening of diffraction peaks with Ni is due to the combined effect of octahedral distortion and reduction in particle size while rulling out any structural phase change. A substantial EB is acquired below spin reorientation transitions which further reduces with higher chemical pressure of Ni. EB field is found to be ∼5.71 kOe at 5 K, revealing a large value compared to similar zero field cooled EB systems. A simple model is proposed based on tunable shell-core magnetic phases to explain these unique EB effects. Present study also aimed to explore the spin and oxidation state of Fe vis a vis magnetic ordering in LaFeO _3 together with consequence of Ni doping.

Keywords

• lanthanum ferrite
• exchange bias
• chemical pressure
• nanocrystal