Spin of Antiparticles
The "antiparticle" is a copy of the "particle" with opposite electric charge. The magnetic dipole moment direction of the "antiparticle" will be the opposite of that of the "particle". Let's place an electron and its antiparticle positron in the same magnetic field. Electron and positron magnetic dipole moments will be aligned in opposite directions. The "spin" for both, however, is 1/2.
When we discussed the "spin direction" we talked about placing electrons in a magnetic field. Now, let's assume there is no external magnetic field and we measure the spin direction. In reality, any such measurement has to involve a magnetic field but let's just assume for the sake of argument that it is a "measurement" of spin direction without specifying how the "measurement" is done. We "measure" the component of electron spin vector along a random direction. As you can guess from the previous discussion, the "spin direction" will either be positively aligned ("up") with the chosen direction or negatively aligned ("down"). Alignment with an angle is not possible. All spin direction measurements are 2-valued. In technical jargon, this is expressed with the statement: quantum mechanical spin operator has 2 eigenvalues.
http://knol.google.com/k/what-is-spin#
The rotating Black Hole has a magnetic moment and creates in strong gravitational field an effect of the gravitomagnetism.
Indirect validations of gravitomagnetic effects have been derived from analyses of relativistic jets. Roger Penrose had proposed a frame dragging mechanism for extracting energy and momentum from rotating black holes.[2] Reva Kay Williams, University of Florida, developed a rigorous proof that validated Penrose's mechanism.[3] Her model showed how the Lense-Thirring effect could account for the observed high energies and luminosities of quasars and active galactic nuclei; the collimated jets about their polar axis; and the asymmetrical jets (relative to the orbital plane).[4] All of those observed properties could be explained in terms of gravitomagnetic effects.[5] Williams’ application of Penrose's mechanism can be applied to black holes of any size.[6] Relativistic jets can serve as the largest and brightest form of validations for gravitomagnetism.
http://en.wikipedia.org/wiki/Gravitomagnetism