In magnetic nanoparticles, anisotropy energy has extra contributions compared to that of the bulk counterparts, being the most relevant surface anisotropy. Here we use pressure to separate core from surface anisotropy in one system of maghemite nanoparticles dispersed in a polymer. The core anisotropy is Kcore=7.7×105 erg/cm3 while the surface anisotropy is KS=4.2×10−2 erg/cm2. This in-one-sample separation is possible due to changes in structurally ordered and disordered ratio, which induce changes in the average magnetic anisotropy energy.

Application of physical pressure to a ferromagnetic bisdiselenazolyl radical leads to a decrease in pi-stack slippage. Initially, this leads to an increase in the ferromagnetic ordering temperature T(C), which reaches a maximum of 21 K near 1 GPa. At higher pressures, as the pi-stacks become more nearly superimposed, the value of T(C) diminishes.