INFLUENCE OF EXTERNAL FIELDS ON SPIN REORIENTATION TRANSITIONS IN UNIAXIAL FERROMAGNETS - II - ULTRATHIN FERROMAGNETIC-FILMS

The field-dependent spin reorientation transition (SRT) in ultrathin f erromagnetic films is discussed. A rather general treatment is present ed which involves the extension of the anisotropy-flow concept to syst ems in an applied magnetic field. Special features of field-induced SR T's are deduced from the general analysis. Emphasis is laid on the exp erimental implications, whereby general features are quantitatively de scribed which are as characteristic as fingerprints and serve to set u p a natural classification of the SRT's in external fields. Special at tention is dedicated to resolving the substantial differences between in-field and spontaneous SRT's; ignoring these differences may result in grave misinterpretations of experimental findings.