Spintronics

Spintronics, which stands for “spin transport electronics” is a branch of electronics that exploits the intrinsic spin of the electrons and their fundamental electronic charge for the various functionalities in solid-state devices. Unlike traditional electronics which rely solely on the charge of the electrons, spintronics utilizes both charge and spin properties for data storage, processing, and communication. Electron spins in Spintronics are used to represent binary data which enables efficient and faster data storage and data processing. It is also useful in creating devices that are energy efficient. One such example is a spin-based transistor which can reduce the consumption of power, leading to greener technology. In this article, we will study about Spintronics in detail.

What is Spintronics?

As the name suggests, Spintronic is nothing but Spin Electronics where we study the intrinsic study of electrons along with its magnetic moment for electronic materials and equipment so that we can achieve high performance and increased integration density compared to the traditional electronics. And we can achieve lower power consumption. as well.

Examples of Spintronics

There are several examples of spintronics devices like :

• spin transistors
• spin diodes
• spin filters
• spin ram
• spin logic gates
• spin oscillators

History of Spintronics

• Early Discoveries (1920s-1930s): The concept of electron spin was first introduced in the 1920s by scientists such as Wolfgang Pauli and Samuel Goudsmit.

• Electron Spin Resonance (ESR): In the 1940s, the development of Electron Spin Resonance spectroscopy allowed for the direct observation of the electron spin properties.

• Giant Magnetoresistance (GMR): The field of spintronics gained significant momentum in the late 1980s when the phenomenon of the Giant Magnetoresistance (GMR) was discovered independently by Albert Fert and Peter Grünberg.

• Nobel Prize (2007): The Albert Fert and Peter Grünberg were awarded the Nobel Prize in Physics in 2007 for the their work on GMR and which marked a breakthrough in spintronics.

Reasons of Evolution

The Spintronics evolved due to growing demand for more efficient and compact electronic devices and traditional electronics faced limitations concerning power consumption and heat generation. The Spintronics emerged as a way to overcome these limitations and enable new functionalities.

Effects of Spintronics

The primary effect of spintronics is manipulation of the electron spin to create novel electronic behavior. This includes the generation of spin currents in which can be used for the data transmission and the utilization of spin-dependent phenomena like giant magnetoresistance for the sensitive magnetic field sensing.

Working of Spintronics

In spintronics, the spin of electrons is used to carry and manipulate information. the Spin currents are generated by the injecting electrons with the specific spin orientations into a device. These spin-polarized currents can then influence the magnetization of magnetic layers leading to various effects like resistance changes in the GMR devices or switching in STT devices.

Spintronics

Spin

Spin is an intrinsic property of subatomic particles (electrons, protons, and neutrons). Spin of subatomic particles are associated with angular momentum. It is a fundamental property of particles in the quantum world, which is not related to actual physical spinning like a planet or a top.

Charge

Charge is a fundamental physical property of matter. It is the property of an object which determines that how a subatomic particle interacts with the electromagnetic fields. Charges are of two types i.e., positive charge (+) and negative charge (-).

Spintronic Memory and Spin Generation

In this section we will study about Spintronics Memory and Spin Generation.

Spintronic memory

The Spintronic memory known as “spin memory” or “spin-transfer torque memory” is a type of the non-volatile memory that utilizes the spin of the electrons to store and retrieve data. Unlike traditional DRAM or NAND Flash memory, spintronic memory retains data even when power is turned off making it highly attractive for the various applications including the computing and storage.

Spin Generation

The Spin generation involves creating a spin-polarized current by the various means such as:

• Spin Injection: This is achieved by injecting spin-polarized electrons from the magnetic material into non-magnetic semiconductor or metal.

• Spin Hall Effect: This effect occurs in materials with the strong spin-orbit coupling leading to separation of the up- and down-spin electrons in the response to an electric field.

• Spin-Orbit Interaction: In certain materials spin-orbit coupling can generate spin polarization by the converting charge currents into the spin currents.

Types of Spintronics

There are four types of Spintronics:

• Giant Magnetoresistance (GMR)
• Spin Transfer Torque (STT)
• Metal-Based Spintronics
• Semiconductor-Based Spintronics

1. Giant Magnetoresistance (GMR)

The Giant Magnetoresistance is a quantum mechanical effect that was discovered independently by the Albert Fert and Peter Grünberg in late 1980s. In the given image, you would visualize layers of the magnetic materials separated by a non-magnetic spacer. The relative orientation of magnetization in the magnetic layers affects the electrical resistance. When the magnetization is parallel , resistance is lower and when it’s antiparallel resistance is higher. This groundbreaking discovery opened up new possibilities in field of the spintronics and revolutionized data storage technology.

Giant Magnetoresistance

2. Spin Transfer Torque (STT)

The given diagram shows a layered structure with a fixed magnetic layer and a free magnetic layer and separated by an insulating layer. A current carrying spin-polarized electrons is shown being injected into free layer and Depending on the relative orientation of the spins in two layers, the spin transfer torque can lead to switching the orientation of free layer.

Spin Transfer Torque (STT)

3. Metal-Based Spintronics

Th Metal-based spintronics primarily involve the manipulation of the electron spin in metallic materials. This approach is often referred to as “giant magnetoresistance” or “spin-valve” technology.

• GMR Devices: The GMR devices consist of alternating layers of the ferromagnetic and non-magnetic metals. When an external magnetic field is applied the relative orientation of magnetic moments in ferromagnetic layers can change.
• Spin-Transfer Torque (STT): The STT is a phenomenon in which the spin of the electrons is transferred to magnetic moments in a material leading to changes in their orientations.

4. Semiconductor-Based Spintronics

The Semiconductor-based spintronics focuses on using the semiconducting materials such as silicon or organic semiconductors to manipulate electron spin. This field offers the potential for the combining traditional electronic logic with the spin-based functionalities.

• Spin Injection and Detection: In semiconductor-based spintronics spins are manipulated using the various techniques such as spin injection from the ferromagnetic contact into semiconductor and spin detection by the measuring spin-polarized electron current.

• Spin Transport: The semiconductor materials can support the transport of the spin-polarized carriers over longer distances.

• Spintronics in Logic and Memory: The Semiconductor-based spintronics can be integrated into the conventional semiconductor devices like transistors to create more energy-efficient logic circuits and non-volatile memory devices.

Properties and Characteristics of Spintronics

There are some properties of Spintronics given below :

Properties

• Spin: The Electrons possess an intrinsic angular momentum or spin in which can be either “up” or “down”.

• Spin-Polarization: The degree to which electrons of a particular spin orientation are present in the material.

• Spin-Orbit Interaction: The coupling between an electron’s spin and its orbital motion leading to the various spin-related phenomena.

Characteristics of Spintronics

There are some characterstics of Spintronics given below :

• Non-Volatility: The Spintronic devices can retain information without continuous power supply.

• Fast Switching: The Spintronics allows for the fast switching between different states due to manipulation of spin.

• Low Power Consumption: The Spin-based operations can be achieved with the lower energy consumption compared to charge-based operations.

Applications of Spintronics

• Magnetic Memory: The Spintronics enables the development of the non-volatile magnetic memories like MRAM .

• Spintronic Transistors: The Spin FETs (Field-Effect Transistors) that use spin-polarized currents for the switching.

• Magnetic Sensors: The High-sensitivity sensors for the magnetic fields in applications like hard drives and compasses.

Example on Spintronics

Demonstrate the spin property of the electrons in spintronics, it is the example of Spintronics.

Demonstrate the spin property of the electrons in spintronics

In this diagram, you would typically see two arrows representing electrons. One arrow pointing upwards indicates electrons with the “spin-up” orientation and while another arrow pointing downwards represents electrons with the “spin-down” orientation. This demonstrates the spin property of the electrons.

Spin Up and Spin Down

Advantages and Disadvantages of Spintronics

Advantages of Spintronics

• Lower power consumption due to reduced heat dissipation.
• Faster data processing and switching.
• Compatibility with the existing semiconductor technology.

Disadvantages of Spintronics

• Complex fabrication processes.
• Limited materials suitable for the spintronics.
• Challenges in maintaining spin coherence over longer distances.

Conclusion

The Spintronics has revolutionized electronics by the incorporating electron spin as a new degree of freedom. It has enabled faster and more energy-efficient devices with the applications ranging from the data storage to magnetic sensing.

FAQs on Spintronics

1. Why is spintronics considered energy-efficient?

The Spintronics uses electron spin in which doesn’t require the continuous flow of the charge reducing power consumption.

2. Can spintronics replace traditional electronics entirely?

The Spintronics complements traditional electronics but doesn’t replace it and both have their unique advantages and applications.

3. How does spintronics relate to quantum computing?

The Spintronics concepts like qubits based on the electron spins contribute to quantum computing’s development.