Oxide interface displaying electronically controllable ferromagnetism

Patent metadata

Field	Value
Publication number	US-2016020382-A1
Application number	US-201514801410-A
Country	US
Kind code	A1
Filing date	Jul 16, 2015
Priority date	Jul 17, 2014
Publication date	Jan 21, 2016
Grant date	—

Abstract

A structure includes an electronically controllable ferromagnetic oxide structure that includes at least three layers. The first layer comprises STO. The second layer has a thickness of at least about 3 unit cells, said thickness being in a direction substantially perpendicular to the interface between the first and second layers. The third layer is in contact with either the first layer or the second layer or both, and is capable of altering the charge carrier density at the interface between the first layer and the second layer. The interface between the first and second layers is capable of exhibiting electronically controlled ferromagnetism.

First claim

What is claimed is:

1 . An electronically controllable ferromagnetic oxide structure comprising:
(a) a first layer comprising SrTiO 3 ; (b) a second layer in contact with the first layer, wherein the second layer has a thickness of at least about 4 unit cells, the thickness being in a direction substantially perpendicular to the interface between the first and the second layers; and (c) a third layer in contact with either the first layer or the second layer or both, wherein the third layer is capable of altering the charge carrier density at the interface between the first and second layers; wherein the interface between the first and the second layers is capable of exhibiting electronically controlled ferromagnetism.

2 . The structure of claim 1 , wherein the second layer comprises at least one of LaAlO 3 , LaTiO 3 , EuTiO 3 , Al 2 O 3 , GaTiO 3 , and LaMnO 3 .

3 . The structure of claim 1 , wherein the interface comprises a TiO 2 -terminated [001] SrTiO 3 surface.

4 . The structure of claim 1 , wherein the third layer comprises at least one of a metallic electrode, a reorientable ferroelectric layer, an electrolyte, a polar adsorbate, a self-assembled monolayer, and the tip of an atomic force microscope probe.

5 . The structure of claim 4 , wherein the metallic electrode comprises at least one of Ti and Au.

6 . The structure of claim 4 , wherein the reorientable ferroelectric layer comprises (Pb,Zr)TiO 3 .

7 . The structure of claim 1 , wherein the thickness is at least about 8 unit cells and not more than about 30 unit cells.

8 . A cross-bar array comprising:
(a) a plurality of oxide structures of claim 1 ; (b) a plurality of bit lines that are substantially parallel to one another and are substantially disposed in a first plane; and (c) a plurality of word lines that are substantially parallel to one another and are substantially disposed in a second plane; wherein:
(i) the first plane is substantially parallel to the second plane;
(ii) each bit line is substantially perpendicular to each word line;
(iii) the third layer of each oxide structure comprises at least a portion of at least one bit line; and
(iv) at least one of the layers of each oxide structure is in contact with at least one word line.

9 . The cross-bar array of claim 8 , wherein:
(a) at least one bit line comprises a layer of a first material and a layer of a second material that is different from the first material; (b) the third layer of at least one oxide structure comprises a layer of the first material and a layer of the second material; and (c) the third layer of the at least one oxide structure comprises at least a portion of the at least one bit line.

10 . A method of electronically weakening or removing a ferromagnetic state at an interface between a first and a second layer of a multi-layered oxide structure, the method comprising establishing a voltage difference between the interface and a material in contact with at least one layer of the multi-layered oxide structure, wherein:
(a) the voltage difference is sufficient to increase the charge carrier density at the interface between the first and second layers of the oxide structure; (b) the first layer comprises SrTiO 3 ; (c) the second layer has a thickness of at least about 4 unit cells, the thickness being in a direction substantially perpendicular to the interface between the first and second layers; and (d) the interface between the first and second layers of the oxide structure is capable of exhibiting electronically controlled ferromagnetization.

11 . The method of claim 10 , wherein:
(a) the voltage difference is about 0.01 to about 15 volts; and (b) the voltage applied to the material in contact with the at least one layer is greater than the voltage applied to the interface.

12 . The method of claim 11 , wherein the voltage difference is about 0.02 to about 6 volts.

13 . The method of claim 10 , wherein the interface comprises a TiO 2 -terminated [001] SrTiO 3 surface.

14 . The method of claim 10 , wherein the second layer comprises at least one of LaAlO 3 , LaTiO 3 , EuTiO 3 , Al 2 O 3 , GaTiO 3 , and LaMnO 3 .

15 . The method of claim 10 , wherein the material in contact with the at least one layer of the oxide structure comprises at least one of a metallic electrode, a reorientable ferroelectric material, an electrolyte, a polar adsorbate, a self-assembled monolayer, and a tip of an atomic force microscope probe.

16 . The method of claim 15 , wherein the metallic electrode comprises at least one of Ti and Au.

17 . The method of claim 15 , wherein the reorientable ferroelectric material comprises (Pb,Zr)TiO 3 .

18 . The method of claim 10 , wherein the thickness is at least about 8 unit cells and not more than about 30 unit cells.

19 . A method of electronically establishing an anisotropic ferromagnetic state substantially in a direction g at an interface between a first layer and a second layer of a multi-layered oxide structure, the method comprising establishing a voltage difference between the interface and a material in contact with at least one layer of the multi-layered oxide structure, wherein:
(a) the voltage difference is sufficient to decrease the charge carrier density at the interface between the first and second layers of the oxide structure; (b) the step of establishing a voltage difference is performed while a magnetic field B substantially in a direction {right arrow over (B)} is present at the interface between the first and second layers; (c) the first layer of the oxide structure comprises SrTiO 3 ; (d) the second layer of the oxide structure has a thickness at least about 4 unit cells thick, the thickness being in a direction substantially perpendicular to the interface between the first layer and second layer; and (e) the interface between the first and second layers of the oxide structure exhibits substantially no ferromagnetization immediately prior to the step of establishing a voltage difference.

20 . The method of claim 19 , wherein:
(a) the voltage difference is about 0.01 to about 15 volts; and (b) the voltage applied to the material in contact with the at least one layer is less than the voltage applied to the interface.

21 . The method of claim 20 , wherein the voltage difference is about 0.02 to about 6 volts.

22 . The method of claim 19 , wherein the interface comprises a TiO 2 -terminated [001] SrTiO 3 surface.

23 . The method of claim 19 , wherein the second layer comprises at least one of LaAlO 3 , LaTiO 3 , EuTiO 3 , Al 2 O 3 , GaTiO 3 , and LaMnO 3 .

24 . The method of claim 19 , wherein the material in contact with the at least one layer of the oxide structure comprises at least one of a metallic electrode, a reorientable ferroelectric material, an electrolyte, a polar adsorbate, a self-assembled monolayer, and a tip of an atomic force microscope probe.

25 . The method of claim 24 , wherein the metallic electrode comprises at least one of Ti and Au.

26 . The method of claim 24 , wherein the reorientable ferroelectric material comprises (Pb,Zr)TiO 3 .

27 . The method of claim 19 , wherein the thickness is at least about 8 unit cells and not more than about 30 unit cells.

Assignees

• Univ Pittsburgh

Inventors

• Levy Jeremy
• Bi Feng
• Irvin Patrick R

Classifications

• G11C11/1675

  Writing or programming circuits or methods · CPC title

• G11C11/161 Primary

  details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell · CPC title

• H01F13/00 Primary

  Apparatus or processes for magnetising or demagnetising ({devices for holding workpieces using magnetic or electric force acting directly on the workpieces B23Q3/15} ; for degaussing ships B63G9/06; for clocks or watches G04D9/00; {recording or erasing of information on magnetic record carriers G11B5/00} ; demagnetising arrangements for colour television H04N9/29) · CPC title

• H01L27/222

  Electricity · mapped topic

• G11C11/165

  Auxiliary circuits · CPC title