Magnetic tunnel junction sensors and methods for using the same

A magnetic sensor system comprising:

• a magnetic sensor device comprising:
• a magnetic sensor array comprising two or more magnetic sensors each comprising:
• two or more magnetic tunnel junction (MTJ) magnetoresistive elements electrically connected to each other in series;
• a first electrode contacting at least a portion of a surface of a first MTJ magnetoresistive element and extending beyond an edge of the surface of the first MTJ magnetoresistive element;
• a second electrode comprising a first end contacting at least a portion of an opposing surface of the first MTJ magnetoresistive element and a second end extending beyond an edge of the opposing surface of the first MTJ magnetoresistive element and contacting at least a portion of a surface of a second MTJ magnetoresistive element;
• and
• an analyte-specific probe bound to a surface of one or more magnetic sensors,
• wherein:
• facing surfaces of the first and second electrodes are only overlapping where they contact the surface and the opposing surface of the MTJ magnetoresistive elements,
• the first MTJ magnetoresistive element comprises a first free layer, the second MTJ magnetoresistive element comprises a second free layer, and the first and second MTJ magnetoresistive elements comprise a common antiferromagnetic layer and a common insulating layer between the antiferromagnetic layer and the first and second free layers, and
• the magnetic sensors are configured to detect a magnetically-labeled analyte in a sample;
• and
• a magnetic field source, wherein at least one of the first and second electrodes contacts less than an entire surface of one or more of the first and second MTJ magnetoresistive elements.

A method for evaluating whether an analyte is present in a sample, the method comprising:

• contacting a magnetic sensor with a magnetically-labeled sample to generate a signal, the magnetic sensor comprising:
• two or more magnetic tunnel junction (MTJ) magnetoresistive elements electrically connected to each other in series;
• a first electrode contacting at least a portion of a surface of a first MTJ magnetoresistive element and extending beyond an edge of the surface of the first MTJ magnetoresistive element;
• a second electrode comprising a first end contacting at least a portion of an opposing surface of the first MTJ magnetoresistive element and a second end extending beyond an edge of the opposing surface of the first MTJ magnetoresistive element and contacting at least a portion of a surface of a second MTJ magnetoresistive element, wherein at least one of the first and second electrodes contacts less than an entire surface of one or more of the first and second MTJ magnetoresistive elements;
• and
• an analyte-specific probe bound to a surface of the magnetic sensor,
• wherein:
• facing surfaces of the first and second electrodes are only overlapping where they contact the surface and the opposing surface of the MTJ magnetoresistive elements,
• the first MTJ magnetoresistive element comprises a first free layer, the second MTJ magnetoresistive element comprises a second free layer, and the first and second MTJ magnetoresistive elements comprise a common antiferromagnetic layer and a common insulating layer between the antiferromagnetic layer and the first and second free layers, and
• the magnetic sensor is configured to detect a magnetically-labeled analyte in the sample;
• obtaining a signal from the magnetic sensor;
• and
• evaluating whether the magnetically-labeled analyte is present in the sample based on the signal.