Magnetoelectric multilayer composites for field conversion

• US 20030197970A1
• Filed: 04/18/2002
• Published: 10/23/2003
• Est. Priority Date: 04/18/2002
• Status: Active Grant

• Current Assignee: Oakland University
• Original Assignee: Oakland University
• Inventors: Srinivasan, Gopalan
• Granted Patent: US 6,835,463 B2
• Time in Patent Office: Days
• US Class Current: 360/77.16
• CPC Class Codes: H01F 1/344 Ferrites, e.g. having a cubic spinel structure (X2+O)(Y23+O3), e.g. magnetite Fe3O4
• CPC Class Codes: H01F 41/0246 Manufacturing of magnetic circuits by moulding or by pressing powder magnetic cores made by moulding or by pressing powder H01F27/255; soft magnetic particles H01F1/20, H01F1/36
• CPC Class Codes: H10N 30/85 Piezoelectric or electrostrictive active materials
• CPC Class Codes: H10N 30/8554 Lead-zirconium titanate [PZT] based
• CPC Class Codes: H10N 35/85 Magnetostrictive active materials
• CPC Class Codes: Y10T 428/1114 having tunnel junction effect
• CPC Class Codes: Y10T 428/1143 with defined structural feature
• CPC Class Codes: Y10T 428/12028 Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, etc.]
• CPC Class Codes: Y10T 428/12465 having magnetic properties, or preformed fiber orientation coordinate with shape
• CPC Class Codes: Y10T 428/12861 Group VIII or IB metal-base component
• CPC Class Codes: Y10T 428/12944 Ni-base component
• CPC Class Codes: Y10T 428/325 Magnetic layer next to second metal compound-containing layer

Abstract

Magnetoelectric multilayer composites comprising alternate layers of a bimetal ferrite wherein one of the metals is zinc and a piezoelectric material for facilitating conversion of an electric field into a magnetic field or vice versa. The preferred composites include cobalt, nickel, or lithium zinc ferrite and PZT films which are arranged in a bilayer or in alternating layers, laminated, and sintered at high temperature. The composites are useful in sensors for detection of magnetic fields (10); sensors for measuring rotation speed, linear speed, or acceleration; read-heads in storage devices by converting bits in magnetic storage devices to electrical signals; magnetoelectric media for storing information; and high frequency devices for electric field control of magnetic devices or magnetic field control of electric devices.

Claims

1. In a magnetoelectric composite comprising at least one piezoelectric composition and at least one magnetostrictive composition as separate layers joined together, the improvement which comprises:

a sintered bimetal ferrite as the magnetostrictive composition, wherein one of the metals is zinc, and wherein the composite has a magnetoelectric voltage coefficient of at least 100 mV/cm Oe.

2. The composite of claim 1 wherein the piezoelectric material is selected from the group consisting of lead zirconate titanate (PZT), lead zincate niobate (PZN), lead zincate niobate lead-titanate (PZN-PT), lead magnesium niobate lead-titanate (PMN-PT), lead lanthanum zirconate titanate (PLZT), Nb/Ta doped-PLZT, and barium zirconate titanate (BZT).

3. The composite of claims 1 or 2 wherein the bimetal ferrite has the formula:

Co<sub>1−

x</sub>Zn_xFe₂O₄

where x is 0.2 to 0.5.

4. The composite of claims 1 or 2 wherein the bimetal ferrite has the formula:

Ni<sub>1−

x</sub>Zn_xFe₂O₄

where x is 0.1 to 0.5.

5. The composite of claims 1 or 2 wherein the bimetal ferrite has the formula:

Li<sub>0.5−

x/2</sub>Zn_xFe<sub>2.5−

x/2</sub>O₄

where x is 0.1 to 0.4.

6. In a method for forming a magnetoelectric composite wherein a combination of a piezoelectric composition and a magnetostrictive composition are joined together in separate layers, the improvement which comprises:

(a) providing a bimetal ferrite powder, wherein zinc is one of the metals, as the magnetostrictive composition;

(b) forming a combination of the powder of step (a) with a powder of a piezoelectric material in the separate layers; and

(c) compressing and sintering the combination of step (b) to form the magnetoelectric composite.

7. The method of claim 6 wherein the piezoelectric material is selected from the group consisting of lead zirconate titanate (PZT), lead zincate niobate (PZN), lead zincate niobate lead-titanate (PZN-PT), lead magnesium niobate lead-titanate (PMN-PT), lead lanthanum zirconate titanate (PLZT), Nb/Ta doped-PLZT, and barium zirconate titanate (BZT).

8. The method of claims 6 or 7 wherein the bi-metal ferrite has the formula:

Co<sub>1−

x</sub>Zn_xFe₂O₄

where x is 02. to 0.5.

9. The method of claims 6 or 7 wherein the bimetal ferrite has the formula

Ni₁₋

xZn_xFe₂O₄

where x is 0.1 to 0.5.

10. The method of claims 6 or 7 wherein the bimetal ferrite has the formula:

Li<sub>0.5−

x/2</sub>Zn_xFe<sub>2.5−

x/2</sub>O₄

where x is 0.1 to 0.4.