Imaging\nthe Thermal Hysteresis of Single Spin-Crossover\nNanoparticles

Abstract

The\nmagnetic hysteresis property during the spin transition of\nspin-crossover (SCO) materials holds great promise for their applications\nin spin electronics, information storage, thermochromic, and nanophotonic\ndevices. Existing studies often measured the averaged property of\na bulk sample consisting of lots of individuals. When considering\nthe significant heterogeneity among different individuals and the\ninevitable interparticle interactions, ensemble measurement not only\nblurred the structure–property relationship but also compromised\nthe intrinsic hysteresis property and cyclability. Herein, we employed\na recently developed surface plasmon resonance microscopy (SPRM) method\nto measure the thermal hysteresis curve of single isolated SCO nanoparticles.\nThe thermal-induced spin transition was found to alter the optical\ncontrast of single SCO nanoparticles, which was optically readout\nusing SPRM in a quantitative, nonintrusive, and high-throughput manner.\nSingle nanoparticle measurements revealed an intrinsic transition\ntemperature that was independent of the temperature scan rate and\nsuperior stability after over 11 000 cycles of single SCO nanoparticles.\nCorrelations between the hysteresis and the size and morphology of\nthe same individuals further uncovered the significant nanoparticle-to-nanoparticle\nheterogeneity with implications for the size–property relationship\nand rational design of SCO materials with improved performance.