|Controlling the magnetic characters co-existing at the novel nanometric multiferroic PrAlxFe1-xO3; 0.0 ⩽ x ⩽ 0.6 via an exchange bias interaction to open a new era of applications Original Research Article |
Available online 4 April 2014
Rasha M. Khafagy, E.H. El-khawas
For the first time, the nanometric multiferroic perovskites PrAlxFe1-xO3;0.0 ⩽ x ⩽ 0.6, were synthesized and extensively studied. XRD results and tolerance factor calculations revealed the distorted orthorhombic single-phase structure for all synthesized samples. HRTEM micrographs for PrFeO3(x=0.0) indicated homogeneous orthorhombic nanoparticles with high local crystallinity and highly ordered lattice planes. Interplanar d-spacing calculated from HRTEM accorded well with the d-values estimated from XRD. Introducing the undersized Al3+cations to the B-site on the expenses of Fe3+cations affected the crystallites’ size negatively and resulted in weak lattice inflation due to the BO6octahedral tilting. As a result, PrAl0.1Fe0.9O3(x=0.1) showed polycrystalline nature with deteriorated lattice arrangements, lower ordering and fair homogeneity. Magnetic hysteresis and DC molar magnetic susceptibility verified that this novel and unique series of nanometric multiferroics carries the antiferromagnetic (AFM) character as a secondary magnetic component inside all of its compositions. The existence of superparamagnetism (SPM) and ferromagnetism (FM) among selected x-values were also verified. PrFeO3showed the superparamagnetic character, after which SPM to FM phase transition was established at x=0.1 with soft magnetic features and improved Ms, Mr and Hc values. Interesting magnetic hardening appeared at x=0.2 up to x=0.4 with further improvement of the magnetic constants. FM to AFM phase transition was reached at x=0.6 with the coexistence of the former two phases with different extents at 0.1 ⩽ x-values ⩽ 0.6. Competition between ferromagnetic and antiferromagnetic sub-lattices lead to a ferrimagnetic-like state and induced a phenomenon of exchange bias interaction which resulted in hysteresis necking at x=0.2 and 0.5. Our results are signatures of a complex magnetic structure considered as a magnetic core-shell-like system or a magnetic multilayer-like system with an exchange interaction between the FM/AFM heterosystems at their interfaces. Ms and Mr values recorded for the present series exceed those reported in literature for RFeO3multiferroics with weak ferromagnetic moment. Each sample in this series showed its own magnetic behavior and can be applied to a specific tailored application. New era of applications are expected for this new multiferroic series of perovskites as exchange bias materials.