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Title:: Large reversible magnetostrictive effect in MnCoSi-based alloys at room temperature

Author(s):: Si Yu; Liu Jun; Yang Hui; Gong Yuanyuan; Xu Feng; (School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, China)

Keywords:: magnetostrictive effect; reversible; tricritical point; phase transition critical field

摘要:: 磁場誘導的相變是實現大磁致伸縮效應的一種有效途徑。有別于傳統磁致伸縮，該效應來源于相變過程伴隨的晶格常數變化。然而，由于一級相變特征，磁致相變產生的磁致伸縮通常伴隨較大的不可逆性，難以應用。本文將介紹一種特殊的磁相變合金MnCoSi。由于具有特殊的三相臨界行為，MnCoSi合金有望在室溫通過磁場誘導的二級相變實現可逆、低場的磁致伸縮效應。而上述效應的實現則依賴于合金三相臨界行為的調控。通過調控，合金的三相點溫度以及相變臨界場降低，室溫磁致伸縮效應源于磁場誘導的二級相變，可逆性提升。本文總結并介紹了調控機理以及部分調控方法，這些方法均能在相變臨界場降低的前提下，實現室溫可逆且較大的磁致伸縮效應。基于三相臨界行為的調控，MnCoSi基合金有望具有媲美于Terfenol-D的磁致伸縮效應，在傳感器、聲納、制動器以及震動馬達等領域具有潛在的應用價值。

Abstract:: It is found that the large magnetostrain can be obtained from the magnetic-field induced first-order transition in some magnetic-phase alloys. The magnetostrain is generated from the lattice parameter alteration during the transition, which is quite different from that in conventional magnetostrictive alloys, such as Terfenol-D. However, due to the first-order nature of the transition, the observed magnetostrain is accompanied by obvious irreversibility. To overcome this drawback, we indicate that large reversible magnetostriction can be fulfilled in MnCoSi-based alloys at room temperature. By tuning tricritical behavior, the temperature of tricritical point and the critical driving field can be reduced. Based on this improvement, the room-temperature magnetostriction is generated from low-field induced second-order transition in MnCoSi-based alloys, which is characterized as high reversibility. We also introduce the mechanism and method of tricritical-behavior-tuning. The magnetostrictive effect in MnCoSi-based alloys is comparable to Terfenol-D, indicating potential applications in sensor, actuator, magnetomechanical relays, etc.