Epitaxial ferromagnetic Ni
View Patent ↗An epitaxial Ni 3 FeN film with unique magnetic properties such as single magnetic domain (even in a large scale 0.5″×0.5″), which rotates coherently in response to the desired switching field with a very sharp transition is described. The magnetic hysteresis loop of this new magnetic nitride is close to the perfect ideal square with the same value of saturation magnetization, remnant magnetization, and magnetization right before switching (domain reversal). The switching field is tunable which make this material more attractive for magneto-resistive devices such as MRAM's, read heads and magnetic sensors.
1. A process for the preparation of epitaxial Ni 3 FeN layer, which comprises:
(a) providing an epitaxial substrate which serves as a nucleation site for epitaxial growth of the Ni 3 FeN layer in a reaction chamber;
(b) optionally providing an epitaxial buffer layer which serves as a nucleation site for epitaxial growth of the Ni 3 FeN layer in a reaction chamber; and
c) sputter depositing the Ni 3 FeN layer onto the substrate or the buffer layer from a source of Ni 81 Fe 19 in a nitrogen atmosphere in a chamber at a reduced pressure and an elevated temperature to produce the epitaxial Ni 3 FeN wherein epitaxial Ni 3 FeN layer exhibits magnetic anisotropy, a single magnetic domain, and an essentially square transition movement upon switching of an external applied magnetic field direction providing a hysteresis loop.
2. The process of claim 1 wherein the substrate for the depositing is Al 2 O 3 (1120).
3. The process of claims 1 or 2 wherein the substrate for depositing is Cu on Nb on Al 2 O 3 (1120).
4. The process of claims 1 or 2 wherein the sputtering takes place at a nitrogen partial pressure between 30-40% of total Argon pressure and at a temperature of about 400° C. or higher.