Magnetic structure and properties of the S=5/2 triangular antiferromagnet α-NaFeO2

The magnetic properties of alpha-NaFeO2 are studied by neutron-diffraction and magnetization measurements. An ordered phase with spins aligned along the b(hex) axis exists at low temperatures (T < 4 K). At intermediate temperatures (4 K < T < 11 K), the system passes through an incommensurate ordered phase before transforming into a short-range-ordered state at higher temperatures that persists up to at least 50 K. Although the short-range ordering does not persist to room temperature according to neutron diffraction, the magnetic susceptibility does not follow the Curie-Weiss behavior, even up to 320 K. This rich magnetic behavior can be understood qualitatively as a competition between different magnetic exchange interactions that are similar in magnitude. The delicate balance between these interactions makes alpha-NaFeO2 a candidate for more detailed theoretical work to understand magnetic behavior in frustrated magnetic systems.