Magnetic Coupling Process Research Articles

Two Mechanisms for Extracting Energy and Angular Momentum from a Rotating Black Hole

Two mechanisms of extracting energy and angular momentum from a rotating black hole, the Blandford-Znajek (BZ) process and magnetic coupling (MC) of a rotating black hole (BH) with the surrounding accretion disk, are discussed in detail by using a modified equivalent circuit. We obtain the same value for the BZ power as given by Lee. The strength of the power and torque produced by the rotating BH in the BZ process are compared with those in MC process. In addition, entropy production on the BH horizon due to the BZ process and that due to MC process are compared and discussed also by using the modified equivalent circuit.

Physical properties and X-ray diffraction of a NiMn 2O 4 single crystal below and above the ferrimagnetic transition at Tc = 145 K

The magnetic and calorimetric measurements of stoichiometric NiMn 2O 4 showed a phase transition at T c = 145 K. The single crystal X-ray diffraction investigations pointed to the purely magnetic nature of the transition. The magnetostriction effect, observed in the temperature dependence of the unit cell volume and persisting above T c , suggested a short-range spin ordering. The cation distribution over the tetrahedral and octahedral sites in the spinel structure has been determined; the inversion parameter v = 0.87. The role of Mn cations in the magnetic coupling process has been discussed. Our results allow the formula to be written with the Mn cations in two oxidation states on the octahedral site: (Ni 1 − v 2+ Mn v 2+) [Ni v 2+ Mn 2 − 2 v 3+ Mn v 4+] O 4

Magnetic Coupling in Crystalline Compounds. A Phenomenological Theory of Magnetism in3dMetals

Magnetic coupling processes are considered in terms of the orbitals which result from the splitting of the $d$ levels by the crystalline field. It is shown that the antiferromagnetic and ferromagnetic structure properties of many crystalline compounds can be qualitatively accounted for on the basis of indirect coupling processes which depend on the overlap of magnetic cation $d$ orbitals with $p$ orbitals of intervening anions and on the electron spin occupation appropriate to the particular cations involved.The orbital approach has also been used in considering the magnetic properties of the $3d$ metals and a coupling mechanism has been proposed which is consistent with much of the magnetic data relating to the iron group metals and their alloys.