To investigate the behavior of the magnetization in a single-domain disk with a uniaxial magnetocrystalline anisotropy, the assumption is made that the magnetization changes its direction by the magnetization curling mode. In this mode, the deviation &thgr; of the spin from thezaxis at(r,&fgr;,z)in the cylindrical coordinate is given by &thgr;=a0+a1(r/R)+a2(r/R)2+a3(r/R)3, whereRis the radius of the disk anda0–a3are coefficients. An equilibrium spin configuration is obtained for a given applied fieldHby finding a set of values ofa0–a3that minimize the magnetic energy of the disk. Carrying out this procedure for variousH, a hysteresis loop and the coercive force are obtained. It is found that the configuration in which the spins deviate from thezaxis can be stable and, therefore, the hysteresis loop is not rectangular, even though an applied field is along thezaxis. The deviation is larger for the spins near the lateral surface of the disk, and the spins near the center do not incline easily. Moreover, for a large magnetocrystalline anisotropy and a large diameter, the magnetization changes its direction upward and downward alternately withr. The nucleation field calculated with the present model agrees well with that of the curling mode in an oblate spheroid. ©1997 American Institute of Physics.