Study On The Magnetic Properties And Exchange Bias Effect Of Pr/Gd Doped YCrO₃

There has been much interest in multiferroic materials in recent years. Researchin this field is of great interest because of the potential uses of materials withsimultaneous ferroelectric and magnetic orderings, which provide a wide range ofapplications, including the field of spintronics, sensors, data-storage media, etc. Inrecent years, the multiferroic behaviors of the rare-earth chromium oxides wereobserved in experiments, and they become the research focus again. In this thesis, weresearch on Y_1-xPr_xCrO₃（0≤x≤0.5） and Y_1-xPr_xCrO₃（0≤x≤0.3） samples, andgive a systematic study of the exotic magnetic properties. The paper is divided into sixchapters and the main contents are as follows:In chapter one, we review the development of multiferroic materials, andsummarize the rare-earth chromium oxides and their abnormal magnetization at lowtemperature. We also give an introduction to the research work of exchange biaseffect in recent years.In chapter two, we introduce the main experimental methods, including thesample’s preparation method, structure analysis, and physical property measurementinstruments.In chapter three, the magnetization of YCrO₃and Y_1-xPr_xCrO₃（0.1≤x≤0.5）were investigated. YCrO₃is a canted antiferromagnet with weak ferromagnetism （TN=140K）. Blow the TN, the M-H measurements indicate a coexistence offerromagnetic and antiferromagnetic phases since each M-H curve is a combinationof a hysteresis loop and a straight line. Negative magnetization has been observed inY_1-xPr_xCrO₃（x=0.1, x=0.2） at low temperature.In chapter four, we focus on the exchange bias effect in Y_0.9Pr_0.1CrO₃. Firstly,the temperature dependence of exchange bias has been studied. Results show that at low temperature, the exchange bias effect is obvious, and it disappears at hightemperature. Furthermore, the cooling field dependence of exchange bias field HEBhas also been studied. Results show that when the cooling field is50Oe, negativeexchange bias can be observed; while when the cooling field is1000Oe, positiveexchange bias can be observed.In chapter five, we study the magnetic properties of GdCrO₃and Y_1-xPr_xCrO₃.For GdCrO₃, two reversions have been observed. The phenomenon of negativemagnetization appears after the first reversion. And a second reversion can beobserved due to the spin reorientation transition of Cr at low temperature. ForY_1-xPr_xCrO₃, Gd3+doping facilitates the negative magnetization phenomenoneffectively. In addition, when external field was increased, the negativemagnetization phenomenon can be suppressed.In chapter six, a summary is given for the thesis and some unsolved problemsare also represented.