The quasiclassical theory of a nanosize point contacts (PC) between two ferromagnets is developed. The maximum available magnetoresistance values in PC are calculated for ballistic versus diffusive transport through the area of a contact. In the ballistic regime the magnetoresistance in excess of few hundreds percents is obtained for the iron-group ferromagnets. The necessary conditions for realization of so large magnetoresistance in PC, and the experimental results by Garcia et al are discussed
@article{arxiv.cond-mat/0207648,
title = {Ballistic versus diffusive magnetoresistance of a magnetic point contact},
author = {L. R. Tagirov and B. P. Vodopyanov and K. B. Efetov},
journal= {arXiv preprint arXiv:cond-mat/0207648},
year = {2009}
}