Advanced material will allow to move heavy objects in harsh environments

Researchers at the Ural Federal University and the Institute of Metal Physics of the Ural Branch of the Russian Academy of Sciences, improved the properties of a magnetostrictive material (a compound of terbium and iron) that is promising for use in various devices: generators of powerful sound and ultrasound, magnetic field and electric current sensors, and actuators such as small devices for micro-movements of heavy objects. The main advantage of this advanced material is that it is resistant to extremely low temperatures (up to -190 ° C). The devices based on this material can be used even in space. The article, described material, was published in the Journal of Alloys and Compounds.

A compound of terbium and iron (terbium ferrite) is a well-known magnetostrictive material. Magnetostriction is an effect in which a material changes its size and shape in an external magnetic field. This property is actively used in various devices, including magnetostrictive actuators. Such devices can be used to very accurately control the movement of any technical elements, such as moving lenses in optical devices. The magnetostriction effect can also appear under high loads. For example, using magnetostriction, it is possible to move multi-ton mirrors of a space telescope without serious efforts.

However, the compound has two disadvantages that limit its active utilization. The first is the limited temperature range at which the compound demonstrates its properties. Scientists have solved this issue. They found that the adding (alloying) of magnesium will extend the interval and make the material suitable for extremely low temperature conditions.

"In our compound, the magnetostriction value at liquid nitrogen temperature (approximately -193°С) is a quarter higher than that of the original compound. This can be useful in devices used in the Far North and even, for example, on Mars, where such temperature is atmospheric. The optical, telescope, and sensor tuning devices used there can be improved with our compound. They will make it possible to maintain the accuracy of debugging devices in conditions of temperature differences, which are characteristic of Mars. At the same time, our compound retains magnetostriction at room temperature, which is not inferior to the original terbium ferrite," explains Aleksander Bartashevich, a Junior Researcher at the M.N. Mikheev Institute of Metal Physics of the Ural Branch of the Russian Academy of Sciences and a co-author of the study.

The second limitation for using the compound in various devices is related to the fact that achieving high values of magnetostriction in terbium ferrite is only possible in a magnetic field larger than the simplest inexpensive electromagnet can create. Scientists emphasize that magnesium reduces the size of the required magnetic field to obtain high magnetostriction values.

"The magnetic field strength required to exhibit material properties varies in oersteds. While the original compound of terbium and iron required a magnetic field of more than 20 kiloeursteds to demonstrate magnetostriction, our compound is able to show good results with a magnetic field of 18. This makes it possible to reduce the electrical consumption of devices based on our compound. Replacing terbium with magnesium also makes it possible to reduce the production price of the compound itself, since rare-earth metals are more expensive than magnesium," adds Nikita Kulesh, Senior Researcher at the Section of Solid State Magnetism, Associate Professor at the Department of Magnetism and Magnetic Nanomaterials at UrFU.

Scientists note that in the study they first substituted the rare-earth terbium for the rare-earth magnesium. Previously, terbium in the compound was replaced by dysprosium, a rare-earth metal that improved the properties of the compound, but did not make it cheaper to produce.

This research was carried out within the framework of the state assignment of the Russian Ministry of Science and Education (topics "Magnet" and "Alloys"), as well as with partial support from the Russian Foundation for Basic Research (project № 20-42-660008) and the government of the Sverdlovsk Region.

Reference

Magnetostrictive materials are widely used in ultrasonic generators and receivers. For example, ultrasonic treatment can be used to clean oil wells, thereby increasing the quality and quantity of oil produced. Also in magnetic field and electric current sensors, active vibration protection devices, magnetoelectric energy converters, strain sensors, actuators, etc.

Magnetostrictive actuators are special short-stroke linear actuators. They operate on the basis of the magnetostrictive effect, i.e. a change in the microstructure and linear sizes of a substance under the influence of a magnetic field. The linear motion of the magnetostrictive actuator is achieved by changing the shape of the material, which provides the highest rigidity. Magnetostrictive materials do not degrade with time and are not afraid of overheating; they recover their properties when they cool down. However, they require a high magnetic field strength, so actuators based on them consume a large current. An important advantage of magnetostrictive actuators is the high rate of continuous cyclic operation.

The applications for magnetostrictive actuators are determined by their features of short-stroke length and high speed. Therefore, they are used for linear movements, e.g. in petroleum equipment, automatic noise and vibration suppressors, spray cleaning systems and vibrating screens. Medical equipment and the aerospace industry are promising areas of application.