Schematic of the scanning magnetoresistance microscope. The sample is placed on a computer controlled translation stage. The magnetoresistive probe is connected to a preamplifier and the signal is filtered and digitized by a lock-in amplifier. A CMOS camera is used to determine the distance between the sensor tip and the sample.
Magnetic field profiles at various distances above the magnetic film edge of a permanent magnetic atom chip measured with the magnetoresistance microscope sensitive to the field component (solid lines). The dotted lines correspond to measurements of the magnetic field at approximately the same distance using an ultracold atom cloud sensitive to the field component. The profiles have been offset for clarity. The relative longitudinal offset between the two sets of measurements is initially unknown and is adjusted once for optimum agreement.
Behavior of the magnetic field roughness above the film edge measured using the magnetoresistance microscope (filled circles) and rf spectroscopy of ultracold atoms (open circles), as a function of distance from the film surface. The solid line is a power-law fit to the magnetoresistance microscope data. The inset shows the dependence of the field roughness on the transverse distance from the film edge for a fixed height of above the film surface.
Optical microscope image of the current-carrying wire atom chip. The two sculptured wires are formed by cutting three wide insulating channels, visible as black lines, into a thick Au layer using femtosecond laser ablation.
[(a)–(c)] Measured out-of-plane component and reconstructed in-plane components of the magnetic field above the current-carrying wire atom chip. [(d)–(f)] Corresponding results of the numerical simulation of the current distribution and the associated magnetic field, based on the geometric dimensions of the wire structure.
Line profile of the magnetic field component parallel to the wire at , i.e., directly above the wire. The solid line represents the field data reconstructed from the MR measurement, while the dotted line shows the simulated values.
One-dimensional (top) and two-dimensional scans (bottom) of the magnetic field produced by a perpendicularly magnetized permanent magnetic lattice with a period of . The scan height and step size for both scans were and , respectively. Both scans are obtained by recording the low pass filtered output of the sensor in a single pass without averaging.
The root mean square deviation of 1000 magnetic field measurements vs integration time (points for data, lines to guide eye). Lines (i) and (ii), sensor stationary at field maximum (inset A) and field gradient maximum (inset B); [(iii) and (iv)], sensor sequentially translating between field maximum (inset A) and field gradient maximum (inset B); (v) background field noise measurement with no wire current.
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