Granted Patent B2

US 12,740,328 · App. 18/129,848 · Granted Sep 15, 2026

Inventors: Cory D. Cress (Springfield, VA); Olaf M.J. van 't Erve (Falls Church, VA); Steven P. Bennett (Owings, MD)

Assignee: The Government of the United States of America, as represented by the Secretary of the Navy

H10N50/85H10B61/00H10N50/01H10N50/10

Abstract

Claims (49)

1 . A method to create a FM/AFM interface in a single layer of FeRh, comprising the steps of:

providing a layer of FeRh film;

wherein the layer of FeRh film has a top portion and a bottom portion;

wherein the layer of FeRh film is an antiferromagnetic (AFM) film;

implanting ions into the top portion of the FeRh film;

creating via the step of implanting ions a ferromagnetic (FM) region in the top region;

controlling via ion mass the thickness of the top portion;

maintaining the antiferromagnetic (AFM) region of the bottom portion; and

creating a FM/AFM interface in the single layer of FeRh.

2 . The method to create a FM/AFM interface in a single layer of FeRh of claim 1 , further comprising the steps of:

controlling via ion energy the thickness of the top portion.

3 . A method of inducing exchange bias by single step irradiation in a single FeRh film for use in a magnetic tunnel junction, comprising the steps of:

providing a layer of MgO;

growing an Epitaxial film of FeRh on the layer of MgO;

implanting ions;

creating near-interfacial pinned uncompensated moments;

forming AFM regions near the interface with the FM region; and

coupling antiferromagnetically the pinned uncompensated moments forming AFM domains aligned with the FM layer.

4 . The method of inducing exchange bias by single step irradiation in a single FeRh film for use in a magnetic tunnel junction of claim 3 , further comprising the steps of:

implanting ions to a depth of about 100 Angstroms to about 350 Angstroms in the FeRh or implanting to about half the thickness of the FeRh.

5 . The method of inducing exchange bias by single step irradiation in a single FeRh film for use in a magnetic tunnel junction of claim 3 , further comprising the steps of:

providing a lattice match with 45° rotation oriented parallel to the 100 cubic plane;

annealing in-situ the epitaxial films of FeRh on the MgO;

wherein the FeRh is in an AFM state; and

forming a FeRh metamagnetic FCC—type L10 phase.

6 . The method of inducing exchange bias by single step irradiation in a single FeRh film for use in a magnetic tunnel junction of claim 3 , further comprising the steps of:

utilizing Fe ions as the ions in the step of implanting ions.

7 . The method of inducing exchange bias by single step irradiation in a single FeRh film for use in a magnetic tunnel junction of claim 3 , further comprising the steps of:

utilizing an ion gun with a FeCl 2 solid precursor as the source of Fe;

implanting the Fe ions at 5 keV using the ion gun; and

creating a Fe dose of 7.4×10 15 Fe/cm 2 .

8 . The method of inducing exchange bias by single step irradiation in a single FeRh film for use in a magnetic tunnel junction of claim 4 , further comprising the steps of:

creating a reduction of thickness of approximately 4 nm;

transitioning a top ~60 Å of the FeRh layer to a FM state; and

maintaining a bottom 250 Å of the FeRh layer in the AFM state.

9 . The method of inducing exchange bias by single step irradiation in a single FeRh film for use in a magnetic tunnel junction of claim 4 , further comprising the steps of:

utilizing He ions as the ions in the step of implanting ions.

10 . The method of inducing exchange bias by single step irradiation in a single FeRh film for use in a magnetic tunnel junction of claim 5 , further comprising the steps of:

creating a He dose of 2×10 16 He/cm 2 ; and

transitioning a top ~200 Å of the FeRh layer to a FM state.

11 . The method of inducing exchange bias by single step irradiation in a single FeRh film for use in a magnetic tunnel junction of claim 3 , further comprising the steps of:

enhancing the Fe 57 isotope fraction via the step of implanting ions; and

controlling the Fe/Rh ratio in the ion implanted region of the film.

12 . The method of inducing exchange bias by single step irradiation in a single FeRh film for use in a magnetic tunnel junction of claim 3 , further comprising the steps of:

setting the direction of the exchange bias by heating only to the metamagnetic transition temperature which is below 450 K.

13 . The method of inducing exchange bias by single step irradiation in a single FeRh film for use in a magnetic tunnel junction of claim 3 , further comprising the steps of:

modifying the dose and the species of the step of implanting ions;

modifying the metamagnetic transition;

allowing the exchange bias to persist below room temperature for high doses or at elevated temperatures for low doses.

Assignments (1)

Continuity (2)

References Cited (17)