Structure And Magnetic Properties Of Novel Rare Earth Transition Metal Intermetallic Compounds

Based on the search for novel experimentation method to study the R-Tpermanent-magnet materials, this thesis deals with a study of the formation,structure, functions of stabilizing element in the compound as well as R-Texchange interaction.1. Experimental Results and Discussions for 3:29 compounds: 1. During our experiment to stabilize the compounds R3 (Fe, M) 29 withelement Cr, as we know that 3:29 compounds are stabilizing phase under hightemperature, which poses difficulty in the preparation of such single-phasesample, this limits the further study and application of such compounds. Sothe main purpose of this experiment is to find the 3:29 phase with method offast quenching. We experimented on seven rare earth elements (R=Gd, Nd,Sm, Dy, Ce, Tb, Y) with fast quenching method, but we didn't find the singlephase of 3:29. 59吉林大学物理学院研究生论文第 60 页 共 63 页 2. This thesis analyzed the reasons why we didn't observe the phaseduring our experimentation. The first reason is that, the speed we used in theexperiment is too fast (25m/s), and this results in the non-crystal state of thecompound. The second reason is that, the radii of transition element and thestabilizing element don't satisfy a certain geometrical condition. The thirdreason is the serious oxidization of the raw and processed materials. 3. Analyzed the main factors that control the structure stability of themetal compounds. Study results show that there are three factors: theelectronics properties, geometrical factors (atom radii) and the electronconcentration. All the elements in the compounds we studied are at the leftside of the Periodic Table, so their electronics properties have little effect onthe structure stability of the compounds, but the geometrical factors havestrong effects on the structure stability.2. Ternary system compound La2Co17-xTix was synthesized with themethod of fast quenching. The structures and magnetic properties ofcompound La2Co17-xTix were studied with X-ray powder diffraction andmagnetic measurement. La-Co binary system can't synthesis 2:17 compounds. By inserting thethird stabilizing element M, ternary compound La2Co17-xTix was obtained withfast quenching method. It has a Th2Zn17 structure; M takes up the 6c crystalposition in the structure. The main factor that controls the structure stability ofM stabilized La2Co17-xTix compound is the geometrical factor. The 60吉林大学物理学院研究生论文第 61 页 共 63 页composition region (0.8 ≤ x ≤ 1.2 ) of La2Co17-xTix compound wasmeasured with X-ray powder diffraction method. In our experiment, we try to obtain the following compounds with fastquenching method. Firstly, by synthesizing the compound that composed of a light rare earthNd and a heavy rare earth Dy, we found that they can compose a 2:17compound. This agrees with the 2:17 compound obtained with annealingmethod. From the point of structure stability, because radius of Ti is big, andradius of Dy is small, so the content of stabilizing element is low. In ourexperiment, we choose Ti=1.0. Because radius of Nd is big, so Ti=0.5. Secondly, we choose R=Nd, Er, Gd, Tb; M= Ti, Al, V to composeR2Fe17-xMx compounds. In Nd2Fe17-xTix compound, we didn't find 2:17compound. The possible reason is that, the rolling speed is too fast or thecontent of the stabilizing element is too high or the fast quenching method cannot be applied in achieving such kind of compounds. For Er2Fe16.5Al0.5,Er2Fe16Al1 compounds, when the stabilizing element Al=0.5, 2:17 compoundscan be obtained. When the stabilizing element Al=1.0, the main component ofthe compound is α-Fe. So we can conclude that, to obtain Er2Fe17-xAlxcompounds, the content of the stabilizing element is low. In R-T compounds,the radii of the atoms affect the stability most. The radius of R atom and theradius of T atom must satisfy a cer...