Theoretical considerations on the anhysteretic remanent magnetization of interacting particles with uniaxial anisotropy

[ 1] The anhysteretic remanent magnetization (ARM) is widely used in rock magnetism and paleomagnetism because of its sensitivity to the domain state of magnetic particles and the close analogy to natural remanent magnetizations. On the other hand, the ARM shares with other weak-field magnetizations the property of being extremely sensitive to magnetostatic interactions. Therefore it is desirable to model the effects of interactions on natural assemblages of magnetic particles. Direct micromagnetic calculations of the ARM acquisition process are not practicable; therefore an analytical approach is used calculate the ARM susceptibility of a system of interacting single-domain (SD) particles. The model is based on a statistical description of the interaction field. The equations obtained have been used to evaluate the dependence of the ARM on the packing fraction of the magnetic particles. The effect of interactions on the anisotropy of ARM (AARM) was evaluated as well. The AARM of densely packed particles is complex and depends critically on the microcoercivity. A physical interpretation of the AARM of highly interacting particles is therefore difficult.