Half Metal Trilayer TMR Reader for Thinner Sensor Design
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Solution Overview
Problem
Current magnetoresistive sensors in hard disk drives are limited by their thickness, which restricts the achievement of higher recording densities due to their minimum thickness of approximately 20 nm, hindering the reduction of playback gap length and thus limiting recording density advancements.
Innovation Solution
A trilayer magnetoresistive sensor structure is developed, comprising an underlayer, a first free layer with a nitride or Heusler ferromagnetic layer, a barrier layer, and a capping layer, which enables anti-parallel coupling and allows for a thinner design while maintaining high recording densities by optimizing magnetic interaction and resistance changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional magnetoresistive sensor structures are used, then the sensor can be manufactured with standard processes, but the sensor thickness remains limited to approximately 20 nm, preventing further reduction of playback gap length
Solution Approach 1:
The sensor is divided into three distinct magnetic layers (first free layer, pinned layer, and second free layer) separated by nonmagnetic spacer layers. This segmentation allows each layer to be optimized independently for thickness and magnetic properties, enabling the total sensor thickness to be reduced below the conventional 20 nm limit while maintaining functional performance through the combined effect of multiple specialized layers
Solution Approach 2:
The patent employs ultra-thin ferromagnetic layers and nonmagnetic spacer layers with thicknesses controlled at the nanometer and sub-nanometer scale. By using thin film deposition techniques to create these flexible, controllable layers, the sensor achieves a total thickness less than 20 nm, breaking the conventional thickness barrier and enabling reduced playback gap lengths for higher recording densities
2Quantity of substance
If the playback gap length is reduced to increase recording density, then higher data storage capacity is achieved, but the sensor thickness becomes the limiting factor that prevents further reduction
Solution Approach 1:
By segmenting the sensor into three functional magnetic layers with distinct roles, the design enables the playback gap length to be reduced independently of the sensor thickness constraint. The segmented structure allows the sensor to maintain adequate magnetic functionality while occupying less space in the playback gap direction, thus enabling higher recording densities without being limited by the conventional 20 nm thickness barrier
Solution Approach 2:
The patent transitions from a conventional single-layer or dual-layer structure to a trilayer configuration, adding a dimensional complexity that allows independent optimization of the playback gap length. This dimensional change in the magnetic layer architecture enables the playback gap to be reduced to enhance recording density while the sensor thickness is managed through the distributed structure of multiple thin layers
3Length of moving object
If anti-parallel coupling is implemented between free layers to enable thinner design, then sensor thickness is reduced, but the magnetic interaction control becomes more complex
Solution Approach 1:
Nonmagnetic spacer layers are introduced as intermediary elements between the ferromagnetic layers. These spacers mediate the magnetic interaction by providing controlled coupling or decoupling between adjacent magnetic layers, enabling anti-parallel coupling configurations. The intermediary spacers simplify the control of magnetic interactions compared to direct layer contact, as they provide a tunable barrier that can be adjusted by thickness to achieve the desired coupling strength and sign
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 trilayer sensor achieves thinner film thicknesses, enabling increased recording densities and reduced playback gap lengths, thereby enhancing data storage capabilities.
Implementation Method 1
The combination of the first and second free layers causes anti-parallel coupling (i.e., J<0) between the magnetic moments of the first and second free layers
Implementation Method 2
a magnetoresistive (MR) read transducer that is deposited between non-magnetic layers and magnetic shield layers
Data Source
AI summary
In an embodiment of the invention, a trilayer magnetoresistive sensor comprises an underlayer on which a first free layer is deposited. A barrier layer is then deposited after which a second free layer is deposited. A capping layer is then deposited above second free layer. The first free layer is a layer which includes at least a layer of a nitride of an element including at least one of Fe, Co, or Ni, or a multiple laminate structure of a layer containing a nitride of an element including at least one of Fe, Co, Ni and another ferromagnetic layer containing at least one of Fe, Co, or Ni. The combination of the first and second free layers causes anti-parallel coupling.