A magnetic thin film is a layer of ferromagnetic or ferrimagnetic material—typically a transition-metal alloy such as permalloy, an amorphous rare-earth transition-metal alloy, or a ferromagnetic oxide—with thickness ranging from nanometres to a few micrometres, deposited onto a non-magnetic substrate so that its magnetic behavior is governed by the constraints of reduced dimensionality and by interfaces rather than by bulk anisotropy alone

A magnetic thin film is a laterally extended layer of magnetically ordered material whose thickness is sufficiently small for reduced dimensionality, surfaces, interfaces, or geometric confinement to significantly influence its magnetic properties relative to those of the corresponding bulk material. Magnetic thin films can comprise ferromagnetic, ferrimagnetic, or antiferromagnetic materials and may be formed on non-magnetic or magnetic substrates, buffer layers, or as individual layers within magnetic/non-magnetic multilayers and heterostructures ^[1][2]. Although magnetic thin films commonly have thicknesses ranging from a few nanometres to several micrometres, there is no universal thickness boundary separating a thin film from a bulk material; the relevant criterion is the extent to which reduced thickness, interfaces, and geometry affect the magnetic state and behavior. The magnetic properties of thin films are determined by the competition among intrinsic exchange interactions, magnetocrystalline anisotropy, shape and magnetostatic anisotropy, surface and interfacial anisotropy, and stress-induced anisotropy

^[1]. In such films, the competition between the intrinsic magnetocrystalline anisotropy, the shape anisotropy imposed by the thin geometry, and the interfacial and stress-induced anisotropy determines the orientation of the magnetization and the conditions for magnetization reversal. Because the thickness is comparable to or smaller than characteristic magnetic lengths such as the exchange length and domain wall width, the film supports stripe or single-domain states, spin structures, and magnetization dynamics that differ from those of the corresponding bulk material. The interfaces with the substrate and adjacent layers further modify the magnetic moment and give rise to interfacial anisotropy and interlayer exchange coupling

^[2][3]. These contributions influence the orientation and stability of magnetization, magnetic domain structures, magnetization reversal, and magnetic dynamics. Domain configurations, including single-domain, multidomain, and stripe-domain states, depend on the balance among exchange, magnetostatic, domain-wall, and anisotropy energies, as well as on the film thickness and lateral dimensions

^[2]. The magnetic thin film is therefore defined as a laterally extended, thin ferromagnetic layer whose magnetic state and reversal are controlled by dimensional, interfacial, and stress anisotropies superimposed on intrinsic exchange interactions ^[3].

. Interfaces and adjacent layers can further modify magnetic properties through interfacial anisotropy, exchange coupling, and other interface-related effects. Magnetic thin films are therefore important components of magnetic recording, spintronic devices, sensors, and other technologies that require controlled magnetic properties at reduced dimensions.