Spectral Noise Analysis for Magnetic Read Head Structures
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Solution Overview
Problem
Magnetic heads with defective read head structures exhibit unpredictable resistivity changes, making it crucial to test for instabilities and noise, particularly to increase recording density in hard drive disks.
Innovation Solution
A testing device applies an external magnetic field to a magnetic head with a read head element, processing signals to generate spectral power density and histograms, characterizing noise characteristics across different frequency ranges and thermal conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If magnetic heads are produced with higher recording density, then storage capacity increases, but noise and instabilities in read head structures increase
Solution Approach 1:
The patent applies preliminary thermal excitation to the read head structure before actual operation to activate and detect potential instabilities and noise. By pre-heating the read head to operating temperature and performing spectral analysis, defective structures are identified before deployment, ensuring only reliable high-density read heads are used.
2Measurement precision
If spectral analysis is performed across multiple frequency ranges, then noise characterization accuracy improves, but testing time increases
Solution Approach 1:
The patent segments the spectral analysis into multiple frequency ranges (e.g., 0-100 MHz, 100-300 MHz, 300-500 MHz) and performs separate power density calculations for each segment. This allows comprehensive noise characterization across the entire spectrum while enabling parallel processing and efficient data analysis, reducing overall testing time compared to analyzing the full spectrum sequentially.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively determines noise characteristics, enabling the qualification and rejection of magnetic heads based on noise patterns, ensuring predictable resistivity changes and improved recording density.
Implementation Method 1
The basic concept of magnetoresistive element is that resistance of such element changes as a function of applied magnetic field. Such elements can be produced by using an anisotropic magnetoresistive effect (AMR) element, a giant magnetoresistive effect (GMR) element such as a spin-valve MR element or a tunnel magnetoresistive effect (TMR) element
Implementation Method 2
An electromagnetic coil 102, which e.g., is a C-core electromagnetic coil with windings or a Helmholtz coil, for producing an external magnetic field that is applied to the composite thin-film magnetic head under test
Data Source
AI summary
A testing device tests a magnetic head with a read head structure including a read head element while applying an external magnetic field to the magnetic head. The testing device receives signals from the read head element and processes the signals to generate a spectral power density for the signals. The spectral power density is characterized for at least one frequency range. The characterization of the spectral power density is used to determine a characteristic of noise from the read head structure. The signals from the read head may be received with different applied magnetic fields and/or before or while thermally exciting the magnetic head. Additionally, a histogram of the signals may be generated and used to determine a second characteristic of the noise.