Permanent magnets are materials that can generate a magnetic field without the need for an external power source. They are widely used in various applications, ranging from electric motors and generators to magnetic sensors and data storage devices. Permanent magnets exhibit several unique features that make them indispensable in many industries. Unlike electromagnets that require a continuous flow of electric current to maintain a magnetic field, permanent magnets retain their magnetic properties even when the power source is removed. This feature makes them suitable for applications where a constant magnetic field is necessary, such as in magnetic storage devices or speakers.
Permanent magnets can possess a high magnetic strength, enabling them to generate strong magnetic fields. Stronger magnets are capable of exerting greater force on magnetic materials, making them ideal for applications where high magnetic forces are required, such as in industrial lifting magnets or magnetic separators. In addition, permanent magnets are known for their stability, meaning their magnetic properties remain consistent over time. They are resistant to demagnetization, meaning they retain their magnetization even in the presence of external magnetic fields. This stability makes permanent magnets reliable for long-term use in various applications.
Permanent magnets come in various shapes and sizes, allowing for versatility in design and application. This flexibility in shape enables their integration into different devices and systems. Permanent magnets exhibit magnetic properties over a broad temperature range, depending on the type of magnet material used. Some magnets, such as neodymium-iron-boron (NdFeB) magnets, cannot maintain their magnetic properties at high temperatures, while others like samarium-cobalt (SmCo) magnets are suitable for use in extreme temperature environments. Due to their ability to generate a magnetic field without the need for an external power supply, permanent magnets contribute to energy-efficient applications. Electric motors and generators that utilize permanent magnets require less energy to operate, leading to improved overall efficiency.
Lastly, permanent magnets can be manufactured in small sizes without sacrificing their magnetic strength. This characteristic is particularly advantageous in the miniaturization of electronic devices, such as smartphones, headphones, or hard disk drives, where space is limited but a magnetic field is still required.
In this project, novel rare-earth free permanent magnets based on α-MnBi were synthesized by severe plastic deformation (SPD) (high-pressure torsion (HPT) processing). The magnetic α-MnBi phase has a high magnetic anisotropy and an increasing coercivity with increasing temperature. Thus, it is also well suited for high temperature applications (i.e. electric motors). If exchange coupled with a soft magnetic phase, the processed permanent magnets could even surpass the magnetic properties of well-established hard magnetic materials. Notwithstanding all described benefits, a commercialization was not realized up to now as synthetization is rather challenging and even more demanding for applications, where bulk materials are inevitable.
