Crystal-field analysis of the magnetization process in a series of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Nd</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Fe</mml:mi></mml:mrow><mml:mrow><mml:mn>14</mml:mn></mml:mrow></mml:msub></mml:mrow><

Yamada, Motohiko; Katô, Hiroaki; Yamamoto, Hirotsugu; Nakagawa, Yasuaki

doi:10.1103/physrevb.38.620

Cited by 277 publications

(130 citation statements)

References 47 publications

Supporting

Mentioning

118

Contrasting

Order By: Relevance

“…Reflecting this difference, the CEF and H ex parameters obtained by Yamada et al are considerably different from ours. To examine the availability of the present method and reliability of the parameters obtained above, we also calculated the K 1 (T ) and K 2 (T ) curves using the parameters given by Yamada et al 18) Except for the behavior of K 2 (T ) below 70 K, we confirmed that the calculated data agree with both the experimental and our calculated results. These results lead us to believe that the present analysis 3/7 Submitted to Applied Physics Express and the parameters obtained here can provide an appropriate characterization for K 1 (T ) and K 2 (T ) at the quantitative level at least above 100 K.…”

supporting

confidence: 82%

“…18) Under the assumption that the exchange field on the 4f electrons is strong enough, by using the CEF parameter A 0 2 , the leading anisotropy constant K 1 can be approximately described by K 1 = −3J(J −1)α r 2 A 0 2 N R , where α is the Stevens factor, J is the total angular momentum, r 2 is the average ofr 2 over the radial wave function of the 4f electrons, and N R is the density of RE ions. Note that the CEF parameter 1/7 is easily affected by circumstances especially around the grain boundaries.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Theoretical evaluation of the temperature dependence of magnetic anisotropy constants of Nd₂Fe₁₄B: Effects of exchange field and crystal field strength

Sasaki¹,

Miura²,

Sakuma³

2015

Appl. Phys. Express

View full text Add to dashboard Cite

To identify the possible mechanism of coercivity (H c ) degradation of Nd-Fe-B sintered magnets, we study the roles of the exchange field acting on the 4f electrons in Nd ions and theoretically investigate how the variation of the exchange field affects the values of the magnetic anisotropy constants K 1 and K 2 . We find that, with decreasing exchange field strength, both values decrease as a result of the lower asphericity of the 4f electron cloud, indicating that the local anisotropy constants might become small around the grain boundaries where the exchange fields are decreased owing to the smaller coordination number.Nd-Fe-B sintered magnets [1][2][3] have the largest maximum energy product among the current magnets and have been widely used for magnetic devices such as voice coil motors in magnetic recording systems. Recently, because of the rapidly growing interest in electric vehicles, much effort has been made to suppress the degradation of the coercivity (H c ) of Nd-Fe-B magnets. However, from an industrial viewpoint, reduction in the usage of Dy is strongly desired, because Dy is a rare metal and the magnetization of the Nd-Fe-B magnets decreases by substituting Dy with Nd owing to the antiparallel coupling between Dy and Fe moments. Realizing Dy-free high-performance Nd-Fe-B magnets requires a further increase of H c in the Nd-Fe-B system by microstructure optimization, [4][5][6][7][8][9][10][11] and therefore, establishing the microscopic foundation for the coercivity mechanism is desired. From a theoretical viewpoint, many works [12][13][14][15][16] have focused on the change of magnetic anisotropy constants around the grain boundary surfaces as a result of the stresses, defects, and change of spatial symmetry. In addition, micromagnetic model calculations have shown that the surface c-plane anisotropy can drastically decrease the coercivity. 17) For these reasons, evaluation of the local anisotropy constants around the grain boundaries and determining their temperature dependence are important to investigate the degradation of the coercivity.With regard to the magnetic anisotropy of rare earth (RE) transition metal compounds, it is believed that the 4f electrons in RE ions are responsible for the main part of the magnetic anisotropy and that the crystalline electric field (CEF) acting on the 4f electrons dominates this property. 18) Under the assumption that the exchange field on the 4f electrons is strong enough, by using the CEF parameter A 0 2 , the leading anisotropy constant K 1 can be approximately described by K 1 = −3J(J −1)α r 2 A 0 2 N R , where α is the Stevens factor, J is the total angular momentum, r 2 is the average ofr 2 over the radial wave function of the 4f electrons, and N R is the density of RE ions. Note that the CEF parameter

show abstract

supporting

confidence: 82%

mentioning

confidence: 99%

Theoretical evaluation of the temperature dependence of magnetic anisotropy constants of Nd₂Fe₁₄B: Effects of exchange field and crystal field strength

Sasaki¹,

Miura²,

Sakuma³

2015

Appl. Phys. Express

View full text Add to dashboard Cite

show abstract

“…A program based on simplifi ed Yamada-Kato model [4] was applied to simulate spin reorientation phenomenon. The procedure was similar to that described in [6,8].…”

Section: Resultsmentioning

confidence: 99%

“…It seems to be interesting to observe these effects also using Mössbauer spectroscopy. The theoretical model, describing the mentioned above processes, was constructed in 1988 by M. Yamada, H. Kato, and Y. Nakagawa [4]. Recently the model was expanded from simple R 2 Fe 14 B to mixed R 2−x R' x Fe 14 B which allows describing compounds like Er 2−x Tb x Fe 14 B.…”

Section: Introductionmentioning

confidence: 99%

Search for canted spin arrangement in Er₂₋ _x Tb _x Fe₁₄B with Mössbauer spectroscopy

et al. 2015

View full text Add to dashboard Cite

Abstract. The materials studied were polycrystalline compounds Er 2−x Tb x Fe 14 B (x = 0.1, 0.2, 0.3, 0.4) which crystallize in a tetragonal lattice and display a variety of spin arrangements. The compounds have been measured with 57 Fe Mössbauer spectroscopy over the temperature range 80-320 K in order to investigate the spin reorientation processes. Each compound was studied in a wide temperature range, with precise Mössbauer scanning in the vicinity of the transition. The set of spectra obtained for a given compound was analyzed using simultaneous fi tting procedure to investigate the infl uence of the transition on the shape of the spectra. The fi tting program was specifi ed to analyze the transition according to the 'two state model': spins fl ip abruptly from initial angle to fi nal arrangement (90° angle). Obtained results suggest that spin reorientation process cannot be described using only the mentioned above model. Additional computer simulations based on the Yamada-Kato model were conducted to determine temperature range and the type of spin alignments in the vicinity of the transition. These theoretical results supported by spectra analysis suggest the existence of intermediate (canted) spin arrangements in the studied compounds. The spin arrangement diagram was constructed.

show abstract

“…The simplifi ed Yamada-Kato model [11] was used to conduct the computer simulation of possible spin arrangements. The program is based on crystal fi eld and exchange parameters, quantum numbers, Curie temperatures, and the anisotropy constant.…”

Section: Computer Simulations -Theoretical Modelmentioning

confidence: 99%

Spin reorientation process in Tm_2–xHo_xFe₁₄B – analysis of conical arrangement based on Mössbauer spectra

et al. 2017

View full text Add to dashboard Cite

Abstract. The spin reorientation process in the Tm 2-x Ho x Fe 14 B series of compounds was studied using 57 Fe Mössbauer spectroscopy over the temperature range 5.2-320 K with a focus on the analysis of conical spin arrangement. Each compound was studied by precise Mössbauer scanning in the vicinity of the transition and during the transition. By applying computer simulations based on the simplifi ed Yamada-Kato model, as well as on some literature data for R 2 Fe 14 B (R = Tm, Ho) compounds, the above series was selected for studies as it contains compounds with different spin arrangements (axial, planar, conical). It was a crucial requirement for obtaining unambiguous angular dependences when applying a simultaneous fi tting procedure of Mössbauer spectra. Such an extended procedure was applied which allowed the temperature dependence of the angle describing the position of the magnetization vector to be obtained. The results were compared with those from theoretical simulations. The spin arrangement diagram was constructed. A conical spin arrangement was confi rmed over a wide temperature range.

show abstract

Crystal-field analysis of the magnetization process in a series ofNd2Fe14<

Cited by 277 publications

References 47 publications

Theoretical evaluation of the temperature dependence of magnetic anisotropy constants of Nd₂Fe₁₄B: Effects of exchange field and crystal field strength

Theoretical evaluation of the temperature dependence of magnetic anisotropy constants of Nd₂Fe₁₄B: Effects of exchange field and crystal field strength

Search for canted spin arrangement in Er₂₋ _x Tb _x Fe₁₄B with Mössbauer spectroscopy

Spin reorientation process in Tm_2–xHo_xFe₁₄B – analysis of conical arrangement based on Mössbauer spectra

Contact Info

Product

Resources

About

Crystal-field analysis of the magnetization process in a series ofNd2Fe14<

Cited by 277 publications

References 47 publications

Theoretical evaluation of the temperature dependence of magnetic anisotropy constants of Nd2Fe14B: Effects of exchange field and crystal field strength

Theoretical evaluation of the temperature dependence of magnetic anisotropy constants of Nd2Fe14B: Effects of exchange field and crystal field strength

Search for canted spin arrangement in Er2− x Tb x Fe14B with Mössbauer spectroscopy

Spin reorientation process in Tm2–xHoxFe14B – analysis of conical arrangement based on Mössbauer spectra

Contact Info

Product

Resources

About

Theoretical evaluation of the temperature dependence of magnetic anisotropy constants of Nd₂Fe₁₄B: Effects of exchange field and crystal field strength

Theoretical evaluation of the temperature dependence of magnetic anisotropy constants of Nd₂Fe₁₄B: Effects of exchange field and crystal field strength

Search for canted spin arrangement in Er₂₋ _x Tb _x Fe₁₄B with Mössbauer spectroscopy

Spin reorientation process in Tm_2–xHo_xFe₁₄B – analysis of conical arrangement based on Mössbauer spectra