Study On The Magnetic Transition Temperature Of Topological Antiferromagnetic Mn₃Sn Thin Films

With the explosive iteration of big data,cloud computing and artificial intelligence,memory,one of the most important electronic devices in this field,continues to develop rapidly,with higher density and lower power consumption.Nowadays,traditional semiconductor memory devices are approaching the limits of Moore’s Law.In contrast,magnetic memory is non-volatile due to the direction of the magnetic moment of the material as the storage medium,and has natural advantages in storage density,energy consumption,and read and write speed,and is expected to perform better in the future.In particular,in addition to the advantages of ordinary magnetic memory,magnetic memory based on antiferromagnet is not easily interfered by magnetic fields and other factors in the external environment because it has no net magnetic moment,and has stronger application potential.Among the many antiferromagnetic materials,topological antiferromagnetic Mn₃Sn has the most application value because of its anomalous Hall resistivity comparable to ferromagnetic materials.However,to date,the preparation of high-quality epitaxial Mn₃Sn films that can be applied to integrated devices has been extremely challenging.The main purpose of this thesis is to prepare topological antiferromagnetic Mn₃Sn films with good epitaxial lattice orientation,and further explore the simple measurement method of the phase transition of the magnetic structure of Mn₃Sn films,so as to solve the problem that ordinary laboratories cannot fully optimize the quality of the prepared Mn₃Sn films by measuring the magnetic structure and their phase transitions due to the inability of ordinary laboratories to have advanced measurement methods such as neutron diffraction.In this process,the following important progress has been made:Firstly,Mn₃Sn thin films were prepared on MgO（110）and Al₂O₃（1（?）02）substrates by Pulsed laser deposition（PLD）.For MgO（110）substrate,XRD data shows that although pure Kagome topology antiferromagnetic Mn₃Sn thin films were prepared on MgO（110）substrate,the crystallization quality of the film is not high,the grain size is small,and it contains two different orientations.For the Al₂O₃（1 （?）02）substrate,systematic XRD,magnetization curves,and magnetic transport performance characterization measurements have shown that the Mn₃Sn thin films we prepared on the Al₂O₃（1（?）02）substrate are all high-quality topological antiferromagnetic films with epitaxial（11（?）0）orientation.Secondly,we systematically studied the longitudinal resistance,magnetization curve,transverse Hall resistance,and magnetic resistance of（11（?）0）oriented Mn₃Sn thin films grown on Al₂O₃（1（?）02）substrate as a function of temperature.Based on the above measurement results,it can be observed that all the magnetic phase transition temperature points below the Néel temperature of the Mn₃Sn film are the phase transition of the inverse triangular antiferromagnetic spin structure to the incommensurate spiral magnetic structure of T₁～275 K,the transition state of the incommensurate spiral magnetic structure to completely incommensurate spiral magnetic structure of T₂～200 K and the completely incommensurate spiral magnetic structure to the spin glass ferromagnetic structure of T_g～50 K.The above results can solve the problem that ordinary laboratories cannot fully optimize the quality of the prepared Mn₃Sn films by measuring the magnetic structure and its phase transition because they cannot have advanced measurement methods such as neutron diffraction.