Giant planar Hall effect in epitaxial Fe 3 O 4 thin films and its temperature dependence

We have investigated the giant planar Hall effect ( ρ x y ) in epitaxial thin films of Fe 3 O 4 grown on MgO (001) substrates with thickness ranging from 5 to 150 nm. A record value at room temperature of ∣ ∣ ρ x y ∣ ∣ ≈ 60   μ Ω   cm was obtained for the 5-nm-thick film. Below room temperature, ∣ ∣ ρ x y ∣ ∣ shows a huge enhancement when crossing the Verwey transition, reaching the value of 16   m Ω   cm at T = 73   K for the 20-nm-thick film. This work demonstrates the potentiality of the planar Hall effect in magnetite thin films for studies of magnetization processes as well as for sensitive low-field detection. The influence of the superparamagnetic tendency for the thinnest films is highlighted. The results are also discussed in the context of fundamental aspects of Fe 3 O 4 below the Verwey transition.