Hybrid hall vector magnetometer

• US 20040217756A1
• Filed: 05/21/2004
• Published: 11/04/2004
• Est. Priority Date: 11/04/2002
• Status: Active Grant

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Miller, Michael, Bennett, Brian, Johnson, Mark B.
• Granted Patent: US 6,917,198 B2
• Time in Patent Office: Days
• US Class Current: 324/202
• CPC Class Codes: G01R 33/07 Hall effect devices
• CPC Class Codes: Y10S 977/853 Biological sample
• CPC Class Codes: Y10S 977/865 Magnetic force probe

Abstract

A modified hybrid Hall effect device is provided which is the combination of a conventional Hall effect device and a second Hall effect device having a Hall plate coupled to a ferromagnetic layer. The hybrid Hall effect device can be used to determine the independent magnetic field vector components comprising a vector magnetic field, such as for determining the {circumflex over (x)} and the {circumflex over (z)} components of a magnetic field, or for measuring the total magnitude of a vector magnetic field of any orientation. The modified Hall Effect device can be adapted for use as a magnetic field sensor for the detection of macroscopic objects that have associated magnetic fields, or for microscopic objects that have been tagged by microscopic magnetic particles. In one specific form, a plurality of hybrid Hall devices are electrically connected together to form an array in which a plurality of rows of hybrid Hall devices are electrically coupled to each other along a current axis, and the array is used for the detection of microscopic objects.

Claims

1-18. -18. (cancelled)

19. A method of calibrating a magnetic force microscope (MFM) tip by measuring vector components of a magnetic field generated by the microscope tip, said method comprising the steps of:

generating an electrical current that flows along a current axis of a conductive substrate,

scanning the microscope tip across a first section of said conductive substrate at a variable height;

generating a first electrical signal along a first voltage axis in response to a vector component of the magnetic field from the microscopic tip acting on the electrical current in said conductive substrate;

detecting said first electrical signal;

measuring said first electrical signal;

recording said first electrical signal with respect to the variable height;

and mapping values of said first electrical signal as a function of the variable height.

20. The method of claim 19, wherein said variable height is from about 0 nm to about 2000 nm.

21. The method of claim 19, further comprising the steps of

scanning the microscope tip across a second section of said conductive substrate at a variable height, said second section including a first ferromagnetic film, and generating a corresponding fringe field at an edge of said first ferromagnetic film in response to vector components of the magnetic field from the microscope tip acting on said first ferromagnetic film, said edge of said first ferromagnetic film located adjacent to a second voltage axis, such that said corresponding fringe field is perpendicular to the current axis in said conductive substrate;

generating a second electrical signal along said second voltage axis in response to said fringe field acting on the electrical current in said conductive substrate;

detecting said second electrical signal-,

measuring said second electrical signal;

recording said second electrical signal with respect to the variable height, and

mapping values of said second electrical signal as a function of the variable height.

22. The method of calibrating a magnetic force microscope of claim 21, further comprising the steps of.

scanning the microscope tip across a third section of said conductive substrate at a variable height, said third section including a second ferromagnetic film, and generating a corresponding fringe field at an edge of said second ferromagnetic film in response to vector components of the magnetic field from the microscope tip acting on said second ferromagnetic film, said edge of said second ferromagnetic film located adjacent to a third voltage axis such that said corresponding fringe field is perpendicular to a second current axis in said conductive substrate;

generating a third electrical signal along said third voltage axis in response to said fringe field acting on the electrical current in said conductive substrate;

detecting said third electrical signal;

measuring said third electrical signal;

recording said third electrical signal with respect to the variable height;

and mapping values of said third electrical signal as a function of the variable height.

23. A method of identifying chemical or biological agents that have been tagged with microscopic magnetic particles and introduced onto a substantially flat surface, by measuring vector components of a magnetic field generated by the magnetic particles, said method comprising the steps of

mounting a Hall device on a scanning probe tip;

generating an electrical current that flows along a first current axis of a conductive substrate of the Hall device;

scanning the chemical or biological agents introduced onto said surface and generating a first electrical signal along a first voltage axis in response to vector components of a magnetic particle˜

s magnetic field acting on the electrical current in said conductive substrate;

detecting said first electrical signal,

recording said first electrical signal; and

mapping values of said first electrical signal with respect to magnetic fields associated with the magnetic particles.

24. The method of claim 23 further comprising the step of measuring said first electrical signal after detecting said first electrical signal.

25. The method claim 23 further comprising the steps of.

generating a second electrical signal along said second voltage axis in response to said fringe field acting on the electrical current in said conductive substrate:

detecting said second electrical signal,

recording said second electrical signal; and

mapping values of said second electrical signal with respect to magnetic fields associated with the magnetic particles.

26. The method of claim 25 further comprising measuring said second electrical signal after detecting said second electrical signal.

27. The method of claim 25, further comprising the steps of.

generating an electrical current that flows along a second current axis of a third section of said conductive substrate;

scanning the chemical or biological agents and generating a fringe field at an edge of a second ferromagnetic film in response to vector components of a magnetic particle'"'"'s magnetic field acting on said second ferromagnetic film, said edge of said second ferromagnetic film located on a third section of said conductive substrate adjacent to a third voltage axis of said conductive substrate, such that said fringe field is perpendicular to a second current axis;

generating a third electrical signal along said third voltage axis in response to said fringe field acting on the electrical current in said conductive substrate;

detecting said third electrical signal.

recording said third electrical signal; and

mapping values of said each electrical signal with respect to magnetic fields associated with the magnetic particles.

28. The method of claim 27 further comprising measuring said third electrical signal after detecting said third electrical signal.

29. A cell array for determining the vector components of an external magnetic field of an object said cell array comprising:

at least one row comprising a plurality of integrated Hall effect devices. each said Hall effect device electrically interconnected along a current axis, each said integrated Hall effect device comprising a conductive substrate having a top surface with a first section for carrying an electrical current, such that a first electrical signal is generated in response to one of the vector components of the external magnetic field acting perpendicularly on an electrical current in said conductive substrate; and

a detector for detecting the presence of each electrical signal.

30. The cell array of claim 29 further comprising a device for measuring a parameter of each electrical signal.

31. The cell array of claim 29, wherein said cell array comprises a plurality of rows.

32. The cell array of claim 29, wherein said conductive substrate comprises a first arm and an opposing second arm, said first arm electrically connected to ground and said second arm electrically connected to a first isolation element, said first isolation element electrically connected to a sense amplifier.

33. The cell array of claim 32, wherein said conductive substrate comprises a first bias arm and an opposing second bias arm, said first bias arm electrically connected to a current source, and said second bias arm electrically connected to a first bias arm of a second Hall effect device, and a second bias arm of said second Hall effect device electrically connected to ground.

34. The cell array of claim 32, wherein said plurality of sense amplifiers are electrically grounded.

35. The cell array of claim 29, wherein each said integrated Hall effect device further comprises:

said top surface further comprises a second section carrying an electrical current. said first section being positioned in close proximity to said second section; and

wherein a first ferromagnetic film having at least two configurable magnetization orientation states, and being disposed over a portion of said second section such that a fringe magnetic field can be generated from an edge of said first ferromagnetic film by vector components of the external magnetic field acting on said ferromagnetic film, and such that a second electrical signal can be generated in response to the fringe magnetic field acting on the electrical current in said conductive substrate.

36. The cell array of claim 35, wherein said conductive substrate and said first ferromagnetic film are separated by an insulating layer.

37. The cell array of claim 35, wherein said conductive substrate comprises a third arm and an opposing fourth arm, said third arm electrically connected to ground and said fourth arm electrically connected to a second isolation element, said second isolation element electrically connected to a further sense amplifier.

38. The cell array of claim ′

37, wherein said each sense amplifier is electrically grounded.

39. The cell array of claim 37 wherein said first isolation element and said second isolation element comprise Schottky diodes.

48. A method of identifying chemical or biological agents that have been tagged with microscopic magnetic particles by measuring vector components of a magnetic field generated by the magnetic particles, said method comprising the steps of

generating an electrical current that flows along a current axis of a conductive substrate forming a plurality of integrated Hall effect devices, each Hall effect device being electrically connected to each other along said current axis,

introducing the chemical or biological agents onto said substrate;

generating a first electrical signal along a first voltage axis in response to vector components of a particle'"'"'s magnetic field acting on said electrical current in said conductive substrate;

detecting each electrical signal;

measuring each electrical signal;

recording each electrical signal;

and mapping values of each electrical signal with respect to magnetic fields associated with the magnetic particles.

49. The method of claim 48 further comprising:

generating an electrical current that flow along a plurality of current axes of a conductive substrate, the conductive substrate comprising a plurality of rows of a plurality of integrated Hall effect devices, each Hall effect device of a respective current axis electrically connected to one another along the respective current axis;

introducing the chemical or biological agent onto said plurality of rows;

generating a plurality of electrical signals along a plurality of voltage axes, respectively, in response to vector components of a particle'"'"'s magnetic field acting on said electrical current in said conductive substrate;

detecting said plurality of electrical signals;

measuring said plurality of electrical signals,

recording said plurality of electrical signals, and

mapping values of said plurality of electrical signals with respect to magnetic fields associated with the magnetic particles.