Avian magnetoreception model realized by coupling magnetite-based   mechanism with radical-pair-based mechanism
  Many animal species were verified to use geomagnetic field for their navigation, but the biophysical mechanism of magnetoreception has remained enigmatic. This paper presents a special biophysical model that consists of magnetite-based and radical-pair-based mechanisms for avian magnetoreception. The amplitude of the resultant magnetic field around the magnetic particles corresponds to the geomagnetic field direction and affects the yield of singlet/triplet state products in the radical-pair reactions. Therefore, in the proposed model, the singlet/triplet state product yields are related to the geomagnetic field information for orientational detection. The resultant magnetic fields corresponding to two materials with different magnetic properties were analyzed under different geomagnetic field directions. The results showed that ferromagnetic particles in organisms can provide more significant changes in singlet state products than superparamagnetic particles, and the period of variation for the singlet state products with an included angle in the geomagnetic field is approximately 180{\deg} when the magnetic particles are ferromagnetic materials, consistent with the experimental results obtained from avian magnetic compass. Further, the calculated results of the singlet state products in a reception plane showed that the proposed model can explain the avian magnetoreception mechanism with an inclination compass. 
Yan Lu and Tao Song
physics.bio-ph