Forming iron nitride hard magnetic materials using chemical vapor deposition or liquid phase epitaxy
A hard magnetic material includes α″ Fe 16 N 2 . In some examples, the hard magnetic material may be formed by a technique utilizing chemical vapor deposition or liquid phase epitaxy.
1. A method comprising:
submerging a substrate in a coating solution comprising a nitrogen-containing solvent and an iron source, wherein the coating solution is saturated with the iron source at a first temperature above a liquidus temperature of an iron-nitrogen mixture to be deposited from the coating solution;
cooling the coating solution to a second temperature to form a supersaturated coating solution, wherein the second temperature is below the liquidus temperature of the iron-nitrogen mixture;
keeping the substrate in the supersaturated coating solution to allow a coating comprising iron and nitrogen to form on the substrate; and
annealing the coating comprising iron and nitrogen to form at least some crystals comprising α″-Fe 16 N 2 .
2. The method of claim 1 , wherein the solvent comprises at least one of ammonium nitrate, an amide, or hydrazine.
3. The method of claim 1 , wherein the iron source comprises at least one of substantially pure iron, FeCl 3 , Fe(CO) 5 , or an iron oxide.
4. The method of claim 1 , wherein the second temperature is between about 600° C. and about 800° C.
5. The method of claim 1 , wherein the coating comprising iron and nitrogen comprises an atomic ratio of iron to nitrogen between about 11.5:1 (iron:nitrogen) and about 5.65:1 (iron:nitrogen).
6. The method of claim 1 , wherein the coating comprising iron and nitrogen comprises an atomic ratio of iron to nitrogen about 8:1 (iron:nitrogen).
7. The method of claim 1 , wherein annealing the layer comprising iron and nitrogen to form at least some crystals comprising α″-Fe 16 N 2 comprises heating the layer at a temperature between about 100° C. and about 220° C. for between about 5 hours and 80 hours.