Scanning Magnetoresistance Microscope Research Articles

Scanning Magnetoresistance Microscopy Analysis of Bit Patterned Media Playback

A scanning magnetoresistance microscope (SMRM) was used to enable recording experiments on bit patterned media prototypes not yet suitable for spin-stand evaluation. The SMRM generates a 2D playback response of the media by “dragging” a recording head across the sample using a piezoelectric nanopositioner. A large-scale parameter optimization technique is applied to extract relevant parameters such as pulse amplitude, pulse width, and pulse position from the 2D playback response. The parameters were analyzed to learn that the pulse response of our recording head cannot be accurately modeled as a Gaussian function. The error in the optimized parameters is dominated by intertrack interference and to a lesser extent measurement resolution and thermal drift.

Quantitative current measurements using scanning magnetoresistance microscopy

We have demonstrated the capability of scanning magnetoresistance microscope (SMRM) to be used for quantitative current measurements. The SMRM is a magnetic microscope that is based on an atomic force microscope (AFM) and simultaneously measures the localized surface magnetic field distribution and surface topography. The proposed SMRM employs an in-house built AFM cantilever equipped with a miniaturized magnetoresistive (MR) sensor as a magnetic field sensor. In this study, a spin-valve type MR sensor with a width of 1 μ m was used to measure the magnetic field distribution induced by a current carrying wire with a width of 5 μ m and a spacing of 1.6 μ m at room temperature and under ambient conditions. Simultaneous imaging of the magnetic field distribution and the topography was successfully performed in the DC current ranging from 500 μ A to 8 mA. The characterized SV sensor, which has a linear response to magnetic fields, offers the quantitative analysis of a magnetic field and current. The measured magnetic field strength was in good agreement with the result simulated using Biot–Savart's law.

Magnetic Field Measurement using Scanning Magnetoresistance Microscope with Spin-Valve Sensor

We developed a new microfabricated cantilever with a spin-valve sensor (MR cantilever) for a scanning magnetoresistance microscope (SMRM). Since the spin-valve sensor has a self-biasing mechanism, it allows the SMRM to respond to the observed magnetic field linearly without any external bias magnetic field, hence making the SMRM more sensitive to magnetic fields. We successfully obtained SMRM images of a magnetic garnet thin film using the new MR cantilever.

Fabrication and Characterization of an MR Cantilever with a Spin-Valve Sensor for a Scanning Magnetoresistance Microscope

We developed a new micro-fabricated cantilever with a spin-valve sensor (MR cantilever) for a scanning magentoresistance microscope (SMRM). Since thespin-valve sensor has a self-biasing mechanism, it allowsthe SMRM to respond to an observed magnetic field linearly without any external bias magnetic field, and itmakes the SMRM more sensitive to magnetic fields. Wehave succeeded in introducing the self-biasing mechanism into the SMRM system by fabricating the spin-valve sensor on a cantilever.

Magnetic Field Imaging by Scanning Magnetoresistance Microscope with MR Cantilever

We developed a micro-fabricated cantilever with an MR sensor (MR cantilever) for use as a scanning magnetoresistance microscope (SMRM). Using a four-point MR cantilever with good signal-to-noise ratio, we have succeeded in imaging the stray field distribution of a magnetic garnet sample. Since the magnetic spatial resolution of the SMRM depends only on the physical dimensions of the MR element, the 5-μm by 1-μm MR element used in this study provided a submicronmeter spatial resolution in one direction of the SMRM.

Scanning magnetoresistance microscopy with a magnetoresistive sensor cantilever

In this work, a cantilever with a magnetoresistive (MR) sensor is fabricated for scanning magnetoresistance microscope, in order to realize the simultaneous imaging of surface topography and stray magnetic field distribution. A constant current flowing through a meander-patterned metal wire produces a defined magnetic field, and the wire is used as a sample to demonstrate the simultaneous imaging and to reveal the field sensitivity of the cantilever. A MR image has been successfully obtained with lateral spatial resolution of a few μm and a field sensitivity (Hmin≈1.7 Oe) at room temperature.

Improvement of the MR Cantilever for Scanning Magnetoresistance Microscope

We have developed the micro-fabricated cantilever with an MR sensor (MR cantilever) for scanning magnetoresistance microscope (SMRM). In order to improve the stability of the MR signal acquisition and the reproducibility of the system, we have proposed a new fabrication procedure for the SMRM cantilever. The MR cantilever with a high field sensitivity is realized and allows us to measure magnetic field quantitatively only for the relatively large external field. However, for the small field detection, superposition of topographic signals on the magnetic signals is not negligible. To avoid this problem, four-terminal SMRM cantilevers were fabricated. In addition, we accomplish to make the cantilever with a high spatial resolution by miniaturizing the MR element.

走査型磁気抵抗効果顕微鏡用カンチレバーの作製と評価

走査型磁気抵抗効果顕微鏡用カンチレバーの作製と評価

走査型磁気抵抗効果顕微鏡用カンチレバーの設計と試作

A variety of techniques have been proposed to measure surface magnetic properties using scanning probe microscopy. The most widely used is magnetic force microscopy (MFM). In many cases, however, it is hard to analyze MFM data quantitatively. A magnetoresistive (MR) device is also a candidate for such a sensor that can operate at room temperature with high sensitivity. Yamamoto et al. have demonstrated a scanning magnetoresistance microscope (SMRM) using a commercially available MR read-head for a hard disk. Since they held the MR head on a slider, there was no feedback system to control the distance between sample and sensor. We made a cantilever for the MR sensor to get the surface topography and magnetic properties simultaneously. Its magnetic field sensitivity with 10-mA sensing current is 90 μV/Oe, and our roughly estimated minimum field resolution is a few mOe (only Johnson noise is assumed with 10-kHz bandwidth at room temperature), which is much better than that of a scanning Hall probe microscope.

Scanning magnetoresistance microscopy (SMRM): Imaging with a MR head

We have developed a new scanning magnetic microscopy that uses commercial magnetoresistive (MR) record/playback heads as sense probes. A high-resolution, linearized positioning stage is used to raster scan a magnetic sample with respect to the MR head while the head is in physical contact with the sample. An upper bound on the spatial resolution of the scanning magnetoresistance microscope (SMRM) is 100 nm in the “downtrack” direction and 1–2 μm in the “crosstrack” direction of the head. Magnetic force microscopy has better spatial resolution than SMRM, but SMRM gives a more quantifiable signal since the MR head response can be calibrated in a uniform external field. Furthermore, SMRM has the unique ability to apply localized fields to the sample via the inductive write element.