Chemical Pressure Induced Strain Control of Magnetic Anisotropy in the Simple Perovskite ϵ-Fe 2 O 3

ϵ-Fe 2 O 3 is an exceptional nanoscale ferrimagnet, distinguished by its high coercivity (μ 0 H c > 2 T) and multiferroic behavior. Realizing its potential in advanced technologies requires precise control of its structural, electronic, and magnetic properties. Here, we report La-doping-induced chemical pressure arising from the larger ionic radius of La 3+ substituting for Fe 3+ that systematically modified the local chemical environments. These dopant-driven lattice strains and modified local chemical environments perturbed exchange pathways, producing a non-monotonic variation in saturation magnetization depending on the specific lattice sites occupied by La 3+ . Magnetic hysteresis concurrently revealed a remarkable rise in coercivity from ∼0.2 T for undoped nanoparticles ( x = 0) to ∼2.3 T at x = 0.072, predominantly resulting from a strain-driven enhancement of magnetocrystalline anisotropy. These results established rare-earth substitution as an effective strategy to engineer strain-mediated changes in the nanomagnetism of ϵ-Fe 2 O 3, offering a practical route to tailor high-coercivity and magnetoelectric properties for device applications.