| Project/Area Number |
08640459
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
固体物性Ⅱ(磁性・金属・低温)
|
|---|
| Research Institution | HIROSHIMA UNIVERSITY |
|---|
Principal Investigator |
FUJII Hironobu Hiroshima University, Faculty of Integrated Arts and Sciences, Professor, 総合科学部, 教授 (30034573)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
EKINO Toshikazu Hiroshima University, Faculty of Integrated Arts and Sciences, Associate Profess, 総合科学部, 助教授 (40185103)
|
|---|
| Project Period (FY) |
1996 – 1997
|
| Project Status |
Completed (Fiscal Year 1997)
|
| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1997: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1996: ¥1,700,000 (Direct Cost: ¥1,700,000)
|
|---|
| Keywords | Interstitial Modified Nitrides / Magnetic Anisotropy / Permanent Magnetism / Nd_2Fe_<17> and Nd_2Fe_<17>N_3 / Y_2Fe_<17> and Y_2Fe_<17>N_3 / Curie Point / neutron diffraction / Single Crystal / 窒化物 / 飽和磁化 |
|---|
| Research Abstract |
One of the methods for fablicating new promising magnetic materials is to interstitially introduce non-metallic atoms like H,B,C or N with small atomic-radius into host compounds. In 1990, the interstitially modified compound Sm_2Fe_<14>N_3 was discovered by Coey and Sun, in which the crystal lattice expands by 6-7 % to accommodate three nitrogens at the interstitial site without changing crystal form, the Curie temperature increases dramatically from 397 K to 752 K,the saturation magnetization increases rapidly to reacch 1.54 T being comparable to Nd_2Fe_<14>B,and the uniaxial magnetic anisotropy is induced to be three times as large as that in Nd_2Fe_<14>B.This fact has attracted a lot of attention for basic and applied scientists.
In this work, we have performed neutron diffraction experiments of Y_2Fe_<17> and Y_2Fe_<17>N_3, and high-field magnetization measurements of single crystals Nd_2Fe_<17>N_3 to clarify the mechanism of improvement of magnetism upon nitrogenation. The results obtained are summarized as follows ; From the neutron diffraction studies, (1) the nitrogen atoms fully occupy the 9e site and the volume expands 6.3 %. (2) The magnetic Fe moment which are the nearest to the 9e-N atoms is the smallest (-2.0 mu_B) in nitride, whereas the Fe moment being the farthest from the N-atoms have the largest moment (-2.9 mu_B). These results indicate strong Fe-N hybridization in the nearest neighbors. From the high-field magnetization measurements of single crystals, (3) the second-order-crystal electric field (CEF) coefficient A_2^0 was estimated to be -500 and -1500 K/a_0^2 at 4.2 K for Nd_2Fe _<17> and Nd_2Fe_<17>N_3. (2) The saturation magnetic moment per formula unit increases from 39.6 mu_B to 45.2 mu_B upon nitrogenation. It is noteworthy that the experimental data obtained using high quality poly- and single-crystals in this work is recognized to be the most reliable and available for thetheorists.
|
