Method of Engineering Single Phase Magnetoelectric Hexaferrite Films

Patent metadata

Field	Value
Publication number	US-2017169946-A1
Application number	US-201615378998-A
Country	US
Kind code	A1
Filing date	Dec 14, 2016
Priority date	Dec 14, 2015
Publication date	Jun 15, 2017
Grant date	—

Abstract

A method of making a ferrite thin film is provided in which a portion of the iron ions in the ferrite are substituted by ions of at least one other metal. The substituting ions occupy both tetrahedral and octahedral sites in the unit cell of the ferrite crystal. The method includes placing each of a plurality of targets, one at a time, in close proximity to a substrate in a defined sequence; ablating the target thus placed using laser pulses, thereby causing ions from the target to deposit on the substrate; repeating these steps, thereby generating a film; and annealing the film in the presence of oxygen. The plurality of targets, the sequence of their ablation, and the number of laser pulses that each target is subjected to, are selected so as to allow the substituting ions to occupy both tetrahedral and octahedral sites in the unit cell.

First claim

1 . A method of making a ferrite thin film in which a portion of the iron ions in the ferrite are substituted by ions of at least one other metal, the substituting ions occupying both tetrahedral and octahedral sites in the unit cell of the ferrite crystal, the method comprising the steps of:
(a) providing a substrate and a plurality of targets; (b) placing each target, one at a time, in close proximity to the substrate in a defined sequence; (c) ablating the target thus situated using laser pulses, thereby causing ions from the target to deposit on the substrate; (d) repeating steps (b) and (c), thereby generating a film; and (e) annealing the film in the presence of oxygen;
wherein the plurality of targets, the sequence of their ablation, and the number of laser pulses that each target is subjected to, are selected so as to allow the substituting ions to occupy both tetrahedral and octahedral sites in the unit cell, whereby the ferrite thin film is produced.

2 . The method of claim 1 , wherein the ferrite is a cubic ferrite.

3 . The method of claim 1 , wherein the ferrite is a hexaferrite of the M-, U-, W-, X-, Y-, or Z-type.

4 . The method of claim 3 , wherein the ferrite is an M-type hexaferrite.

5 . The method of claim 4 , wherein the M-type hexaferrite has the composition Sr 2+ Co x 2+ Ti 3−0.5x 4+ Fe 8 3+ O 19 2− , wherein x is from 1.2 to 3.5.

6 . The method of claim 5 , wherein x is 2.0.

7 . The method of claim 6 , wherein a first target and a second target are provided, the first target being SrFe (4−δ) Ti 0.5δ Co 0.5δ Co 0.5δ O 7 , which is used to form an R block in the unit cell, wherein δ is 0 or 0.2.

8 . The method of claim 7 , wherein the second target is Fe (1+0.25δ) Ti 0.5(1−0.25δ) Co 0.5(1−0.25δ) O 3 , which is used to form an S block in the unit cell, wherein δ is 0or 0.2.

9 . The method of claim 8 , wherein the laser pulses used for ablation of the first and the second targets are unequal in number.

10 . The method of claim 9 , wherein the substrate is heated to 600° C.

11 . The method of claim 10 , wherein step (e) is carried out at 1050° C. for 40 minutes.

12 . A ferrite thin film made according to the method of claim 1 .

13 . (canceled)

14 . The ferrite of claim 12 , wherein the ferrite is a hexaferrite of the M-, U-, W-, X-, Y-, or Z-type.

15 . The hexaferrite of claim 14 , wherein the hexaferrite is an M-type hexaferrite.

16 . The M-type hexaferrite of claim 15 having the composition Sr 2+ Co x 2+ Ti 3−0.5x 4+ Fe 8 3+ O 19 2− , wherein x is 1.2 to 3.5.

17 . The M-type hexaferrite of claim 15 having the composition Sr 2+ Co x 2+ Ti 3−0.5x 4+ Fe 8 3+ O 19 2− , wherein x is 2.0.

18 . The M-type hexaferrite of claim 17 having the composition Sr 2+ Co x 2+ Ti 3−0.5x 4+ Fe 8 3+ O 19 2− , wherein, two targets, a first target and a second target are provided for its preparation, the first target being SrFe (4−δ) Ti 0.5δ Co 0.5δ O 7 , which is used to form an R block in the unit cell, δ being 0 or 0.2.

19 . The M-type hexaferrite of claim 18 having the composition Sr 2+ Co x 2+ Ti 3−0.5x 4+ Fe 8 3+ O 19 2− , wherein the second target is Fe (1+0.25δ) Ti 0.5(1−0.25δ) Co 0.5(1−0.25δ) O 3 , which is used to form an S block in the unit cell, δ being 0 or 0.2.

20 . The M-type hexaferrite of claim 19 having the composition Sr 2+ Co x 2+ Ti 3−0.5x 4+ Fe 8 3+ O 19 2− , wherein the laser pulses used for ablation of the first and the second targets are unequal in number.

21 .- 33 . (canceled)

34 . An electromagnetic device comprising the ferrite thin film according to claim 12 .

35 . (canceled)

Assignees

• Univ Northeastern

Inventors

• Vittoria Carmine

Classifications

• H01F10/08

  characterised by magnetic layers ({H01F10/32 takes precedence } ; applying thin magnetic films to substrates H01F41/14) · CPC title

• H01F41/183 Primary

  Sputtering targets therefor · CPC title

• C23C14/28 Primary

  by wave energy or particle radiation (C23C14/32 - C23C14/48 take precedence) · CPC title

• H01F41/22

  Heat treatment; Thermal decomposition; Chemical vapour deposition · CPC title

• H01F10/20

  Ferrites · CPC title