Long-range order parameter of single L10-FePd nanoparticle determined by nanobeam electron diffraction: Particle size dependence of the order parameter

Abstract

The long-range order (LRO) parameter (S) of single isolated L10-FePd nanoparticle was determined by quantitative analysis of nanobeam electron diffraction (NBD) intensities and intensity calculations considering the multiple scattering of electrons. The obtained order parameters of the nanoparticles larger than 8nm are distributed around the mean LRO parameter (S¯=0.79) which was determined by selected area electron diffraction intensity analysis, while the parameters slightly decreased gradually as the particle size decreased below about 8nm (S=0.60–0.73). The low degree of order in very small particles is responsible for the coercivity decrease of the L10 nanoparticles in smaller-sized regions. Quantitative NBD intensity analysis is quite useful for the determination of the LRO parameter of individual L10-FePd single crystalline nanoparticle. Experimental conditions required for NBD analysis are presented in detail and the possible experimental errors of the determined LRO parameters are discussed.