Magnetic field sensor with colossal magneto-resistive material contained within the coil of an oscillator

• US 6,304,083 B1
• Filed: 09/15/1998
• Issued: 10/16/2001
• Est. Priority Date: 09/15/1998
• Status: Expired due to Fees

• Current Assignee: U.S. Army Tacom-Ardec Attn: Amsta-Ar-Gcl
• Original Assignee: The United States Of America As Represented By The Secretary Of The Army
• Inventors: Owens, Frank
• Primary Examiner(s): STRECKER, GERARD R
• Application Number:
  US09/153,674
• Time in Patent Office: 1,127 Days
• Field of Search: 324/236, 324/244, 324/249, 324/252, 324/258, 324/260, 324/327, 324/345, 331/65, 360/110, 360/111, 360/113, 360/123, 360/125-127, 360/318, 360/326, 340/551, 235/449
• US Class Current: 324/258
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• CPC Class Codes: G01R 33/02 Measuring direction or magnitude of magnetic fields or magnetic flux G01R33/20 takes precedence
• CPC Class Codes: G11B 2005/3996 large or giant magnetoresistive effects [GMR], e.g. as generated in spin-valve [SV] devices
• CPC Class Codes: G11B 5/3903 using magnetic thin film layers or their effects, the films being part of integrated structures

Abstract

Sensors, systems and methods for measuring magnetic field strengths in both AC and DC magnetic fields by using CMR material in tunable, radio-frequency LC oscillators are disclosed.

Claims

1. In a sensor that uses frequency tuning over a range of about 1 KHz to about 10 MHz to determine the strength of a magnetic field and which has at least one tunable, radio-frequency LC oscillator with an induction coil, wherein the improvement comprises:

a colossal magnetic resistance (CMR) material contained within said induction coil, the CMR material being ferromagnetic at about or above about room temperature and whose permeability is sufficiently sensitive to external magnetic fields such that the presence of the field will produce a discernable change in the inductance and corresponding frequency of the LC oscillator.

2. The sensor of claim 1 where the frequency change of the oscillator is proportional to the permeability of the CMR material.

3. The sensor of claim 1 being adapted to measure the strength of an external magnetic field selected from an AC magnetic field and combinations of AC and DC magnetic fields.

4. The sensor of claim 1 where the CMR material is a sintered perovskite.

5. The sensor of claim 1 where the CMR material is sintered La_1-xSr_xMnO₃ and x is greater than 0.25.

6. The sensor of claim 1 where the CMR material is sintered La_0.7A_0.3MnO₃.

7. The sensor of claim 1 where the CMR material is ferromagnetic at up to about 370 degrees Kelvin.

8. In an array of sensors having at least two sensors that use frequency tuning to determine the strength of a magnetic field, each sensor using frequency tuning over a range of about 1 KHz to about 10 MHz to determine the strength of the magnetic field and having at least one tunable, radio-frequency LC oscillator with an induction coil wherein the improvement comprises:

a colossal magnetic resistance (CMR) material contained within said induction coil, the CMR material being ferromagnetic at about or above about room temperature and whose permeability is sufficiently sensitive to external magnetic fields such that the presence of the field will produce a discernable change in the inductance and the corresponding frequency of the LC oscillator.

9. In a compact and sturdy magnetometer having a self contained power source and at least one sensor that uses frequency tuning over a range of about 1 KHz to about 10 MHz to determine the strength of a magnetic field and which has at least one tunable, radio-frequency LC oscillator with an induction coil, wherein the improvement comprises:

a colossal magnetic resistance (CMR) material contained within said induction coil, the CMR material being ferromagnetic at about or above about room temperature and whose permeability is sufficiently sensitive to external magnetic fields such that the presence of the field will produce a discernable change in the inductance and the corresponding frequency of the LC oscillator.

10. In a recording head containing at least one sensor that uses frequency tuning over a range of about 1 KHz to about 10 MHz to determine the strength of a magnetic field and which has at least one tunable, radio-frequency LC oscillator with an induction coil, wherein the improvement comprises:

a colossal magnetic resistance (CMR) material contained within said induction coil, the CMR material being ferromagnetic at about or above about room temperature and whose permeability is sufficiently sensitive to external magnetic fields such that the presence of the field will produce a discernable change in the inductance and the corresponding frequency of the LC oscillator.