Magneto optic kerr effect magnetometer for ultra-high anisotropy magnetic measurements

Patent metadata

Field	Value
Publication number	US-9348000-B1
Application number	US-201313836466-A
Country	US
Kind code	B1
Filing date	Mar 15, 2013
Priority date	Dec 20, 2012
Publication date	May 24, 2016
Grant date	May 24, 2016

Abstract

A resistive electromagnet assembly comprises a pair of coils with a gap defined between the coils. The resistive electromagnet assembly is configured to generate a field having a magnetic flux density of at least about 4 Tesla and at a sweep rate to complete a hysteresis loop in less than about 1 minute. A support assembly is configured to support a sample of magnetic material within the gap. An optics module is configured to expose a test region of the magnetic material sample to an optical beam probe while the test region is subjected to the field and to receive a reflected beam from the test region. A processor is coupled to the optics module and configured to measure one or more properties of the magnetic material using the received reflected beam.

First claim

What is claimed is:

1. An apparatus, comprising:
a resistive electromagnet assembly comprising a pair of coils with a gap defined between the coils, the resistive electromagnet assembly configured to generate a field having a magnetic flux density of at least about 4 Tesla and at a sweep rate to complete a hysteresis loop in less than about 1 minute;
a support assembly configured to support a sample of magnetic material having a coercivity of at least 20 kOe within the gap;
an optics module configured to expose a test region of the magnetic material sample to an optical beam probe while the test region is subjected to the field and to receive a reflected beam from the test region; and
a processor coupled to the optics module and configured to measure one or more properties of the magnetic material using the received reflected beam, the processor further configured to measure the one or more properties at each of a plurality of locations on the sample at a rate of one hundred locations within five minutes.

2. The apparatus of claim 1 , wherein the field has a magnetic flux density of between about 4 and 5.5 Tesla.

3. The apparatus of claim 1 , wherein the sweep rate to complete the hysteresis loop is less than about 10 seconds.

4. The apparatus of claim 1 , wherein the sweep rate to complete the hysteresis loop is between about 2 and 10 seconds.

5. The apparatus of claim 1 , wherein the sample of magnetic material is disposed on a disk substrate having a diameter ranging from about 45 mm to about 100 mm.

6. The apparatus of claim 1 , wherein the measured one or more magnetic properties comprises at least one of coercivity and nucleation field at the test region.

7. The apparatus of claim 1 , wherein the measured one or more magnetic properties comprises at least one of switching field distribution and uniformity.

8. An apparatus, comprising:
a resistive electromagnet assembly comprising a pair of coils with a gap defined between the coils;
a support assembly configured to support a sample of magnetic material having a coercivity of at least 20 kOe within the gap, the resistive electromagnet assembly configured to generate a field having a magnetic flux density to cause the magnetic material to reach saturation and at a sweep rate to complete a hysteresis loop in less than about 1 minute;
an optics module configured to expose a test region of the magnetic material sample to an optical beam probe while the test region is subjected to the field and to receive a reflected beam from the test region; and
a processor coupled to the optics module and configured to measure one or more properties of the magnetic material using the received reflected beam, the processor further configured to measure the one or more properties at each of a plurality of locations on the sample at a rate of one hundred locations within five minutes.

9. The apparatus of claim 8 , wherein the sample of magnetic material has a coercivity of between about 20 and 45 kOe.

10. The apparatus of claim 8 , wherein the sample of magnetic material has a coercivity of at least 40 kOe.

11. The apparatus of claim 8 , wherein the field has a magnetic flux density of between about 4 and 5.5 Tesla.

12. The apparatus of claim 8 , wherein the sweep rate to complete the hysteresis loop is less than about 20 seconds.

13. The apparatus of claim 8 , wherein the sweep rate to complete the hysteresis loop is between about 2 and 10 seconds.

14. The apparatus of claim 8 , wherein the measured one or more magnetic properties comprises at least one of coercivity and nucleation field at the test region.

15. The apparatus of claim 8 , wherein the measured one or more magnetic properties comprises at least one of switching field distribution and uniformity.

16. A method, comprising:
subjecting a sample of magnetic material having a coercivity of between about 20 and 45 kOe to a field having a magnetic flux density of at least about 4 Tesla and at a sweep rate to complete a hysteresis loop in less than about 30 seconds, the field to cause a test region of the magnetic material to reach saturation;
exposing the test region to an optical beam probe while the test region is subjected to the field;
receiving a reflected beam from the test region; and
measuring one or more properties of the magnetic material using the received reflected beam at each of a plurality of locations on the sample at a rate of one hundred locations within five minutes.

17. The method of claim 16 , wherein the sweep rate to complete the hysteresis loop is between about 2 and 10 seconds.

18. The method of claim 16 , wherein the sample of magnetic material is supported by a disk substrate, and the method further comprises performing the subjecting, exposing, receiving, and measuring at a plurality of test regions at varying radii of the disk substrate and at a rate of about 2 seconds to about 10 seconds for each test region.

19. The method of claim 16 , wherein the measured one or more magnetic properties comprises at least one of coercivity, nucleation field, switching field distribution, and uniformity.

Assignees

• Seagate Technology Llc

Inventors

• Pressesky Jason L
• Ju Ganping

Classifications

• G01R33/0325 Primary

  using the Kerr effect · CPC title