Seed Layer Hysteresis Suppression in Magnetoresistive Sensors
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Solution Overview
Problem
Conventional magnetic field sensors, particularly Tunnel Magneto Resistive (TMR) devices, suffer from performance limitations due to undesirable hysteresis effects, which persist even after modifying the free layer design to reduce magnetic coercivity.
Innovation Solution
Incorporating a seed layer with one or more CoFe layers, optionally with an Ru layer, to introduce texturing and additional crystalline anisotropy, which cancels magnetic coercivity and removes hysteresis at low fields in TMR stacks, thereby improving sensor accuracy by linearizing the magnetic response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the free layer design is modified to reduce magnetic coercivity, then the magnetic coercivity is reduced, but hysteresis effects persist
Solution Approach 1:
A seed layer is introduced as an intermediary component between the substrate and the TMR stack. This seed layer contains specific crystallographic orientations that induce preferred orientation in the free layer, thereby reducing hysteresis effects without requiring modification of the free layer design itself.
Solution Approach 2:
The invention changes the crystalline structure parameters of the seed layer, specifically incorporating layers with (100) or (110) crystallographic orientations. This parameter change in the seed layer's crystal structure translates to improved magnetic properties in the free layer, reducing hysteresis while maintaining the original free layer design.
2Object-generated harmful factors
If a seed layer with CoFe layers is added to suppress hysteresis, then hysteresis effects are reduced, but the device complexity increases
Solution Approach 1:
The seed layer is segmented into multiple thin layers with specific compositions and thicknesses (e.g., alternating CoFe and Ru layers). Each layer contributes specific properties that collectively achieve hysteresis suppression, allowing the function to be distributed across multiple simple components rather than one complex layer.
Solution Approach 2:
The seed layer uses composite material structures combining CoFe and Ru layers. This composite approach leverages the complementary properties of each material - CoFe for magnetic properties and Ru for structural stability and epitaxial growth - to achieve hysteresis suppression with a relatively simple overall structure.
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 seed layer effectively suppresses hysteresis effects, leading to more consistent resistance changes with magnetic field variations, enhancing the linearity of the resistance/magnetic field relationship and increasing sensor accuracy, especially when operating at fields lower than the seed-induced anisotropy.
Implementation Method 1
the seed layer introduce an additional crystalline anisotropy which provides hysteresis suppression
Implementation Method 2
the CoFe in the seed layer results in a change in texturing of the whole multilayer, and in particular, of the free layer which is responsible for the low-field response of the TMR which governs the magnetic coercivity of the TMR stack
Implementation Method 3
a seed layer with one or more CoFe layers, optionally with an Ru layer, to introduce texturing and additional crystalline anisotropy, which cancels magnetic coercivity and removes hysteresis at low fields in TMR stacks
Implementation Method 4
Tunnel magnetoresistance (TMR) is a magnetoresistive effect that occurs in a magnetic tunnel junction (MTJ) that includes two ferromagnetic layers separated by an insulator. Electrons tunnel from one ferromagnetic layer into the other due to a quantum mechanic effects
Data Source
AI summary
Methods and apparatus for a magnetoresistive (MR) sensor including a seed layer having a CoFe layer for canceling hysteresis in the MR sensor. The MR stackup can include a free layer and a reference layer. The seed layer having CoFe provides a desired texturing of the stackup to cancel hysteresis effects.