Perpendicular Magnetic Recording Write Head With Heater and Heat Sink
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Solution Overview
Problem
In perpendicular magnetic recording systems, the switching time for the main pole of the write head from one magnetization direction to another is a limiting factor at high data rates, primarily due to the slow intrinsic time-constant of magnetization reversal, leading to a loss of write flux.
Innovation Solution
A write head design featuring a heater made of high resistivity material on one side of the main pole and a heat sink on the opposite side, creating a temperature gradient that increases the damping of the ferromagnetic material, thereby enhancing the switching speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the main pole uses conventional ferromagnetic material without temperature gradient, then the material maintains stable magnetic properties, but the switching time from one magnetization direction to another is slow, limiting data rate
Solution Approach 1:
The patent applies temperature gradient as a controllable parameter to change the magnetic damping properties of the ferromagnetic material. By heating one side of the main pole and maintaining the other side at lower temperature, the Gilbert damping constant is enhanced transiently, which accelerates the magnetization reversal process and reduces switching time, directly resolving the contradiction between stable magnetic properties and fast switching speed
Solution Approach 2:
The heating element is activated periodically during the writing process to create transient temperature gradients that coincide with the magnetization reversal cycles. This periodic thermal excitation enhances damping only when needed during switching, allowing fast switching speed while maintaining stable magnetic properties during data storage phases
2Loss of time
If a heater is applied to increase damping and switching speed, then the switching time decreases, but the device complexity increases due to additional heater and heat sink components
Solution Approach 1:
The heater element serves multiple functions: it acts as a heating element to create temperature gradient, functions as a damping enhancement mechanism during switching, and can be integrated with existing write head structures. The heat sink is formed using existing magnetic shield or pole structure that naturally conducts heat away, reducing the need for separate dedicated heat sink components and thereby minimizing additional device complexity
Solution Approach 2:
The patent merges the heater and heat sink functions into the existing write head structure. The heater is integrated adjacent to the main pole, and the heat sink is formed using the magnetic shield or pole structure itself, which naturally conducts heat away. This merging approach achieves the desired temperature gradient while minimizing additional components and structural complexity
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 increased damping results in faster switching speed of the write head, enabling higher data rates by reducing the rise time of the write field when switching magnetization direction.
Implementation Method 1
The heater is formed of high resistivity material and is connected to a power source. During writing, power is applied to the heater, which causes a relatively large temperature gradient across the main pole from the heater to the heat sink.
Implementation Method 2
a heat sink is located on the opposite side of the main pole
Implementation Method 3
The increase in damping of a ferromagnetic material by a temperature gradient has been explained as due to the magnetic analog of the well-known Seebeck effect. Brechet et al., 'Evidence for a Magnetic Seebeck Effect', PHYSICAL REVIEW LETTERS 111, 087205 (2013).
Data Source
AI summary
A perpendicular magnetic recording write head includes a heater on one side of the pole tip of the main pole and a heat sink on the opposite side of the pole tip. The heater is formed of high resistivity material and is connected to a power source. During writing, power is applied to the heater, which causes a relatively large temperature gradient across the pole tip from the heater to the heat sink. The temperature gradient increases the damping of the ferromagnetic material of the main pole during writing, which increases the switching speed of the main pole.