CoFe-Doped TMR Free Layer for Low-Coercivity Magnetic Sensing
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Solution Overview
Problem
High flux CoFe alloys used in TMR elements tend to have high coercivity, making the free layer magnetically harder and less sensitive, which is a drawback for high-density magnetic recording applications.
Innovation Solution
Doping a small amount of elements like hafnium (Hf) or tantalum (Ta) into the high flux CoFe layer to suppress long-range order and induce an amorphous state, resulting in a magnetically soft layer for the TMR element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If high flux CoFe alloy is used in TMR element, then magnetic moment is improved, but coercivity increases making the layer magnetically harder
Solution Approach 1:
The patent changes the chemical composition parameters of the CoFe alloy by introducing dopant elements (Ru, Rh, Ir, Os, Pt, Au, or Cu) at controlled concentrations (0.1-10 at%). This compositional parameter change modifies the electronic structure and magnetic properties, achieving a reduction in coercivity while preserving the high magnetic moment characteristic of CoFe alloys.
Solution Approach 2:
The patent creates a composite alloy system by combining CoFe with dopant elements from the ruthenium group or copper. This composite material approach leverages the high magnetic moment of CoFe while the dopant elements contribute to reducing coercivity through modified exchange interactions and suppressed magnetic anisotropy, resulting in a magnetically soft yet high-moment free layer.
2Reliability
If high coercivity free layer is used, then magnetic stability is improved, but sensitivity decreases
Solution Approach 1:
By adjusting the dopant concentration and type in the CoFe alloy, the patent optimizes the balance between magnetic stability and sensitivity. The dopant-induced changes in magnetic anisotropy and exchange coupling allow the free layer to maintain sufficient stability while becoming more responsive to external magnetic fields, thereby improving sensitivity for high-density recording detection.
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 doping process achieves a magnetically soft and anisotropic TMR reader sensor with low coercivity (Hc 2˜4 Oe) and high dR/R ratio (>110% at RA 0.3), enhancing sensor performance and allowing for thinner TMR stacks.
Implementation Method 1
doping a small amount of an element (e.g., hafnium (Hf), tantalum (Ta), yttrium (Y)) in a high flux CoFe layer of a tunnel magnetoresistance (TMR) element. The small amount of dopant can suppress a long-range order in the CoFe film.
Implementation Method 2
The reading elements of HDD heads can be based on the magnetoresistance effect, which refers to a change in resistance induced by the application of an external magnetic field.
Implementation Method 3
An HDD head can include a tunnel magnetoresistance (TMR) sensor that comprises a magnetic sensor utilizing a TMR element
Implementation Method 4
As an example, co-sputtering can be used to form CoFeHf and CoFeTa alloys.
Data Source
AI summary
The present embodiments relate to a tunnel magnetoresistance (TMR) element. The TMR element can include a free layer comprising a metallic alloy that is doped using a dopant element. In some instances, the metallic alloy comprises a cobalt-iron (CoFe) alloy. The present embodiments relate to doping a small amount of an element (e.g., hafnium (Hf), tantalum (Ta), Yttrium (Y)) in a high flux CoFe layer of a tunnel magnetoresistance (TMR) element. The small amount of dopant can suppress a long-range order in the CoFe film. The amorphous state of a CoFe alloy can be induced by the dopant and result in a magnetically soft layer. A resistance of the TMR element can be modified based on an application of an external magnetic field to the free layer and the pin layer.