Spin Selectivity of Chiral Mesostructured Iron Oxides with Different Magnetisms.

ABSTRACT

Spin selectivity physically depends on either magnetic materials with strong internal magnetic fields or symmetry-breaking materials with large spin-orbit coupling (SOC). However, the spin selectivity of symmetry-breaking magnetic materials is not understood. Herein, the spin selectivity of iron oxides with different magnetisms arising from varying spin alignment is investigated. Chiral mesostructured films of Fe3 O4 (CMFFs), γ-Fe2 O3 (CMγFs), and α-Fe2 O3 (CMαFs), which share the same mesostructure, are prepared by a controllable calcination process of chiral mesostructured FeOOH films (CMOFs) grown on the substrate via an amino acid-induced hydrothermal route. CMFFs and CMγFs with ferrimagnetism exhibit magnetic field-dependent and simultaneously chirality-independent magnetic circular dichroism (MCD) signals, while CMαFs with antiferromagnetism exhibit chirality-dependent, magnetic field-independent MCD signals. It is speculated that the competitive effect between the spin alignment-induced and chirality-induced effective magnetic fields determines the energy splitting of opposite spins in the materials with different magnetisms.