Research Of Magnetism And Exchange Bias Of Sm₂Co₁₇Rare Earth Permanent Magnetic Films

SmCo rare earth permanent magnetic materials have high magnetic anisotropy,low temperature coefficient and good temperature characteristics,which has been widely used in mobile phones,computers,cars,space shuttles,weapons and equipment,etc..The research on SmCo rare earth permanent magnetic thin film materials has important application value and rich scientific significance.In this paper,SmCoCr/Cu/Cr thin films were prepared on SiO₂ substrates by pulsed laser deposition?PLD?method,and the SmCo thin films are mainly in the form of SmCo 2:17 alloy phase,which has a stable crystal structure at room temperature.We studied the structure,magnetic properties,magnetic properties and temperature characteristics of the films by changing the content of different elements and annealing temperature.Moreover,the magnetic exchange bias effect of Sm₂Co₁7/Cr thin films was studied,and the mechanism was discussed.In order to optimize the structure and magnetic properties of Sm₂Co₁7 thin films,we can find some useful theoretical and experimental conclusions.The obtained results are following:1.SmiCo17 films doped with Cr elements based on SiO₂ substrates were prepared by pulsed laser deposition?PLD?technique,and the films has the stable SmCo 2:17 alloy phase structure at room temperature.The effects of preparation process on the growth and crystallization quality were studied,the process conditions of 2:17 alloy phase structure were explored and optimized.The experiment found that in the background of the vacuum degree of 4×10-5 Pa,growth temperature of 400?,keep the laser pulse energy of 190mJ/plus and frequency of 8Hz,Sm and Co elements controlled by the deposition time,can obtain SmCo 2:17 alloy phase crystal structure,which lays the foundation for the preparation of doped Sm₂Co₁7 alloy thin film.2.The effect of structure and magnetic properties have been investigated by analyzing the content of Sm in the SmCo/Cr film and the content of Cr in the antiferromagnetic layer.The experiment found that the increasing of the content of Cr in the antiferromagnetic layer will weak the magnetic of SmCo/Cr thin film.While the film became the best after adding Cr.The appropriate doping of the amount of Cr can get a good structure and guarantee the coercivity.At the same time,with the increase of the content of Sm,the growth of Sm₂Co₁7 phase was be inhibited,and the coercivity and saturation magnetization decreased.Therefor the amount of Sm must be right.In addition,it was found that it was beneficial to the growth of Sm₂Co₁7 phase by adding a Cu substrate before the preparation of the SmCo/Cr film.The structure and magnetic properties of Sm₂Co₁7 thin films were studied by adjusting the annealing temperature.It is found that with the increase of annealing temperature,the growth of Sm₂Co₁7 phase is better,and the coercive force of the film is also improved obviously.3.In the study of the exchange bias phenomenon,we found that the temperature change will lead to the competition of the ferromagnetic phase and antiferromagnetic?SmCo?phase?Cr?,thereby the competition will affect the exchange bias field of Sm₂Co₁7 films;after doping the Cr,the exchange bias field of Sm2CO17 thin films become bigger,illustrating the amount of Cr can enhance the ferromagnetic layer?SmCo?pinning,which can reduce the impact of competition of the ferromagnetic phase?SmCo?and antiferromagnetic phase?Cr?and make the exchange bias phenomenon be more obvious;With the increase of the thickness of magnetic layer,the exchange bias phenomenon is weakened,which is consistent with the HE?1/tFM theory;With the increase of annealing temperature,the change of the saturation magnetization is not large,but the bias field appeared the phenomenon of diminishing.So it is very important to select an appropriate annealing temperature under the high coercivity and degree of crystallinity.