- Email: [email protected]
A note on Dr. J.L. Snoek
Materials Science and Engineering A 370 (2004) 9–11
A note on Dr. J.L. Snoek Masahiro Koiwa∗ Department of Materials Science and Engineering, Faculty of Engineering, Kyoto University, Yoshida-Honmachi, Sakyo-ku, Kyoto 606-8501, Japan Received 12 July 2003
Abstract J.L. Snoek is the eponym of the renowned relaxation effect: the Snoek peak, which is associated with the redistribution of carbon atoms in the bcc iron lattice under the application of the oscillatory stress. A brief review of the Snoek effect and a sketch of Snoek’s life are given; the latter is based on two Dutch articles. © 2003 Elsevier B.V. All rights reserved. Keywords: Snoek peak; Internal friction; Magnetic ferrites
which appeared in Dutch physics journal [1], and an article in technical weekly describing the Philips contribution in the ferrite research [2].
2. A review of the Snoek effect
1. Introduction The Snoek peak is the relaxation phenomenon associated with the reorientation of interstitial solute atoms in the body-centered cubic metals, under the application of oscillatory stress, first found for carbon in iron. The effect is probably most fully investigated and well understood among a variety of relaxation phenomena. The effect or peak is termed after the name of the researcher who proposed its mechanism. Yet not many people know Dr. L.J. Snoek himself and his scientific activities other than the internal friction study. In this paper, a brief review of the discovery and subsequent researches of the Snoek effect, and a brief sketch of Snoek’s life are given. The latter is based on the obituary, ∗
Tel.: +81-77-573-7112; fax: +81-77-573-7112. E-mail address: [email protected] (M. Koiwa).
0921-5093/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2003.08.067
In early work [3] it was observed that the damping of steel tuning forks goes through a maximum as a function of temperature and that the location of this maximum is dependent upon the frequency of the fork. Snoek [4] showed that interstitial solutes were essential to this damping peak by demonstrating that the effect no longer occurred when all traces of carbon and nitrogen were removed. Two years later he [5] developed the theory of preferential distribution of interstitial carbon and nitrogen atoms. In his theory Snoek assumes that interstitial positions occupied by carbon and nitrogen atoms are at the centers of the cell edges, i.e. positions of the type (1/2, 0, 0), and at the face centers, which are equivalent positions. Although the iron lattice is cubic, the local symmetry of these interstitial positions is tetragonal. Thus the interstitial position (1/2, 0, 0) is closer to the two neighboring iron atoms along the [1 0 0] axis than to the four other neighboring iron atoms. The [1 0 0] direction may therefore be regarded as the tetragonal axis of the (1/2, 0, 0) interstitial position. Similarly, every interstitial position has associated with it a tetragonal axis, which is parallel to one of the three principal 1 0 0 axes. If the directions of the cube axes are designated as x, y
10
M. Koiwa / Materials Science and Engineering A 370 (2004) 9–11
and z, respectively, the interstitial sites may be designated as x, y or z sites according to the direction in which maximum distortion is produced. Under zero stress, the three kinds of interstitial sites are occupied in a random fashion; each type of site, therefore, has one-third of the total number of interstitials. The application of a tensile stress in the z-direction, for example, will lower the energy for atoms in z sites as against x and y sites. Such a tensile stress will, therefore, produce a redistribution of atoms such that the z sites are occupied preferentially. The generality of the Snoek mechanism has been demonstrated by the observation of effects, in other bcc lattices containing interstitial solutes, similar to those in ␣-iron. Thus Kˆe investigated relaxation effects due to carbon and oxygen [6] and also nitrogen [7], in tantalum. Further investigation of carbon in tantalum and also in niobium has been carried out by Wert [8]. The presence of small amounts of substitutional alloying elements considerably affects the profile of the internal friction versus temperature curves in the vicinity of the Snoek peak [9]. The theory of the Snoek effect in such ternary alloys has been developed by Koiwa [10]. Examination of relaxation profiles provides a method for quantitative analysis of the interaction between substitutional and interstitial solute atoms; for details, readers are referred to reviews of the subject [11,12]. Nowadays, the term “the Snoek effect” is used in a wider sense, implying the relaxation phenomenon associated with reorientation of isolated solute atoms in any crystal lattice or even in amorphous structure.
3. A brief sketch of Snoek’s life [1,2] Jacobus Louis Snoek was born on May 18, 1902 in Utrecht. He attended the 3-year high school at Utrecht and the pedagogic academy at Harlem, but he did not choose a career in education. In 1921 he began his study in Utrecht, where he got his Ph.D. degree in 1929 with a thesis: “Testing quantum mechanics for hydrogen by means of absorption measurements in the Balmer series”. On 1 April 1929 he joined the Philips company and during 21 years he worked at the Physical Laboratory at Eindhoven. During this period he gave valuable contributions to the development of technically important materials as well as to the understanding of phenomena in solids. In the beginning he worked on acoustics, in particular on carbon microphones, next he collaborated with van Arkel for some years on dielectric properties. One of the results was the manifold quoted equation of van Arkel and Snoek. Around 1934 he entered the subject of the ferromagnetism and for many years this was his main area of work. In the beginning he was mainly involved in the magnetic properties of rolled nickel–iron ribbon, which shows a peculiar texture, is magnetically strongly anisotropic and has longitudinally very favorable properties for application in pupin coils and
filter coils. In this area he collaborated with W.G. Burgers, who investigated the crystallographic part. In 1933 Snoek (together with E.J.W. Verweij) started a project on ferrites, which, because of a lack of results, was frozen. In 1940, Snoek continued the research and at last Philips developed a number of modern ferrite materials for coil cores. In the spring of 1946 a patent was asked on Ni–Fe oxide ferrite, which came on the market under the name of Ferroxcube. Even more successful was Ferroxdure, which appeared in 1950. After all Ferroxcube and Ferroxdure were used for diverse applications, varying from wireless sets and transformers to electro motors. They caused a genuine revolution. A coil which had a volume of half a liter in 1936, was in 1960 only just 5 cm3 . With its research of ferrites and the ensuing materials Philips scored a great international success. But the scientific glory was reaped somewhere else. In 1970 the Frenchman Louis Eugène Néel obtained the Nobel Prize for his theories of ferromagnetism. It is said that Néel based his work for a big deal on Philips’ research. In this area the number of publications of Snoek is rather small, but a good overview of his work can be found in a book, published at Elsevier’s: “New developments in ferromagnetic materials”. Snoek’s work did not only lead to a rather revolutionary development in high frequency technique, but also to interesting new physical views. The interpretation of the phenomenon that losses increase rapidly on approaching a certain frequency limit, as a gyromagnetic resonance in effective fields, which correspond with the crystal anisotropy, can be considered as the crown of his work. From a purely physical point of view, his finest work might be the discovery and explanation of the so-called diffusion damping in solids: the Snoek effect, as described in a separate section. Snoek was a skilled experimentalist: not a great experimental virtuoso, who turned into quite new ways, but a person, who was able to choose effectively the methods to obtain results fast and reliably. His enormous power and the strong concentration—obsession almost—with which he engaged in a subject, is characteristic. Thereby he did not let himself be stopped by rejections and criticism of other people: his strength was that he tackled the problems in an original and unconventional way. If he might sometimes get on the wrong track, his perseverance and his physical intuition brought him at last to valuable results. Because of his obsessiveness he was not always an easy colleague, yet, just because of that, he often could throw a surprising light, also on problems of other persons; thus he inspired many people. In the spring of 1948 he carried out a slowly ripened decision; he emigrated to the United States of America, where he joined a private research laboratory, Horizons Ltd. His stay there was too short to perform great work; Dr. J.L. Snoek died in a car accident on the 3 December 1950. His age was 48.
M. Koiwa / Materials Science and Engineering A 370 (2004) 9–11
Acknowledgements The author wishes to thank Dr. C. Tuijn of University of Amsterdam, who found the two articles [1,2] and kindly prepared the English translations.
References [1] H.B.G. Casimir, N.T. v. N., XVII (1951) 1. [Journal of the Dutch Physical Society]. [2] G. van Nifterik, Technisch Weekblad, 22 May 1996.
[3] [4] [5] [6] [7] [8] [9] [10]
11
E. Woodruff, Phys. Rev. 16 (1903) 321. J. Snoek, Physica 6 (1939) 591. J. Snoek, Physica 8 (1941) 711. T.S. Kˆe, Phys. Rev. 74 (1948) 9. T.S. Kˆe, Phys. Rev. 74 (1948) 914. C.A. Wert, J. Appl. Phys. 21 (1950) 1196. L.J. Dijkstra, R.J. Sladek, Trans. Metal. Soc. AIME 197 (1953) 69. M. Koiwa, Philos. Mag. 24 (1971) 81, 107, 539, 799; M. Koiwa, Philos. Mag. 25 (1972) 701. [11] H. Numakura, M. Koiwa, J. Phys. IV 6 (1996) C8–97. [12] H. Numakura, M. Koiwa, in: A. Wolfenden, V.K. Kinra (Eds.), M3D III Mechanics and Mechanism of Material Damping, ASTM Standard Technical Publication 1304, American Society for Testing and Materials, West Conshohocke, PA, 1998, p. 383.
A note on Dr. J.L. Snoek Masahiro Koiwa∗ Department of Materials Science and Engineering, Faculty of Engineering, Kyoto University, Yoshida-Honmachi, Sakyo-ku, Kyoto 606-8501, Japan Received 12 July 2003
Abstract J.L. Snoek is the eponym of the renowned relaxation effect: the Snoek peak, which is associated with the redistribution of carbon atoms in the bcc iron lattice under the application of the oscillatory stress. A brief review of the Snoek effect and a sketch of Snoek’s life are given; the latter is based on two Dutch articles. © 2003 Elsevier B.V. All rights reserved. Keywords: Snoek peak; Internal friction; Magnetic ferrites
which appeared in Dutch physics journal [1], and an article in technical weekly describing the Philips contribution in the ferrite research [2].
2. A review of the Snoek effect
1. Introduction The Snoek peak is the relaxation phenomenon associated with the reorientation of interstitial solute atoms in the body-centered cubic metals, under the application of oscillatory stress, first found for carbon in iron. The effect is probably most fully investigated and well understood among a variety of relaxation phenomena. The effect or peak is termed after the name of the researcher who proposed its mechanism. Yet not many people know Dr. L.J. Snoek himself and his scientific activities other than the internal friction study. In this paper, a brief review of the discovery and subsequent researches of the Snoek effect, and a brief sketch of Snoek’s life are given. The latter is based on the obituary, ∗
Tel.: +81-77-573-7112; fax: +81-77-573-7112. E-mail address: [email protected] (M. Koiwa).
0921-5093/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2003.08.067
In early work [3] it was observed that the damping of steel tuning forks goes through a maximum as a function of temperature and that the location of this maximum is dependent upon the frequency of the fork. Snoek [4] showed that interstitial solutes were essential to this damping peak by demonstrating that the effect no longer occurred when all traces of carbon and nitrogen were removed. Two years later he [5] developed the theory of preferential distribution of interstitial carbon and nitrogen atoms. In his theory Snoek assumes that interstitial positions occupied by carbon and nitrogen atoms are at the centers of the cell edges, i.e. positions of the type (1/2, 0, 0), and at the face centers, which are equivalent positions. Although the iron lattice is cubic, the local symmetry of these interstitial positions is tetragonal. Thus the interstitial position (1/2, 0, 0) is closer to the two neighboring iron atoms along the [1 0 0] axis than to the four other neighboring iron atoms. The [1 0 0] direction may therefore be regarded as the tetragonal axis of the (1/2, 0, 0) interstitial position. Similarly, every interstitial position has associated with it a tetragonal axis, which is parallel to one of the three principal 1 0 0 axes. If the directions of the cube axes are designated as x, y
10
M. Koiwa / Materials Science and Engineering A 370 (2004) 9–11
and z, respectively, the interstitial sites may be designated as x, y or z sites according to the direction in which maximum distortion is produced. Under zero stress, the three kinds of interstitial sites are occupied in a random fashion; each type of site, therefore, has one-third of the total number of interstitials. The application of a tensile stress in the z-direction, for example, will lower the energy for atoms in z sites as against x and y sites. Such a tensile stress will, therefore, produce a redistribution of atoms such that the z sites are occupied preferentially. The generality of the Snoek mechanism has been demonstrated by the observation of effects, in other bcc lattices containing interstitial solutes, similar to those in ␣-iron. Thus Kˆe investigated relaxation effects due to carbon and oxygen [6] and also nitrogen [7], in tantalum. Further investigation of carbon in tantalum and also in niobium has been carried out by Wert [8]. The presence of small amounts of substitutional alloying elements considerably affects the profile of the internal friction versus temperature curves in the vicinity of the Snoek peak [9]. The theory of the Snoek effect in such ternary alloys has been developed by Koiwa [10]. Examination of relaxation profiles provides a method for quantitative analysis of the interaction between substitutional and interstitial solute atoms; for details, readers are referred to reviews of the subject [11,12]. Nowadays, the term “the Snoek effect” is used in a wider sense, implying the relaxation phenomenon associated with reorientation of isolated solute atoms in any crystal lattice or even in amorphous structure.
3. A brief sketch of Snoek’s life [1,2] Jacobus Louis Snoek was born on May 18, 1902 in Utrecht. He attended the 3-year high school at Utrecht and the pedagogic academy at Harlem, but he did not choose a career in education. In 1921 he began his study in Utrecht, where he got his Ph.D. degree in 1929 with a thesis: “Testing quantum mechanics for hydrogen by means of absorption measurements in the Balmer series”. On 1 April 1929 he joined the Philips company and during 21 years he worked at the Physical Laboratory at Eindhoven. During this period he gave valuable contributions to the development of technically important materials as well as to the understanding of phenomena in solids. In the beginning he worked on acoustics, in particular on carbon microphones, next he collaborated with van Arkel for some years on dielectric properties. One of the results was the manifold quoted equation of van Arkel and Snoek. Around 1934 he entered the subject of the ferromagnetism and for many years this was his main area of work. In the beginning he was mainly involved in the magnetic properties of rolled nickel–iron ribbon, which shows a peculiar texture, is magnetically strongly anisotropic and has longitudinally very favorable properties for application in pupin coils and
filter coils. In this area he collaborated with W.G. Burgers, who investigated the crystallographic part. In 1933 Snoek (together with E.J.W. Verweij) started a project on ferrites, which, because of a lack of results, was frozen. In 1940, Snoek continued the research and at last Philips developed a number of modern ferrite materials for coil cores. In the spring of 1946 a patent was asked on Ni–Fe oxide ferrite, which came on the market under the name of Ferroxcube. Even more successful was Ferroxdure, which appeared in 1950. After all Ferroxcube and Ferroxdure were used for diverse applications, varying from wireless sets and transformers to electro motors. They caused a genuine revolution. A coil which had a volume of half a liter in 1936, was in 1960 only just 5 cm3 . With its research of ferrites and the ensuing materials Philips scored a great international success. But the scientific glory was reaped somewhere else. In 1970 the Frenchman Louis Eugène Néel obtained the Nobel Prize for his theories of ferromagnetism. It is said that Néel based his work for a big deal on Philips’ research. In this area the number of publications of Snoek is rather small, but a good overview of his work can be found in a book, published at Elsevier’s: “New developments in ferromagnetic materials”. Snoek’s work did not only lead to a rather revolutionary development in high frequency technique, but also to interesting new physical views. The interpretation of the phenomenon that losses increase rapidly on approaching a certain frequency limit, as a gyromagnetic resonance in effective fields, which correspond with the crystal anisotropy, can be considered as the crown of his work. From a purely physical point of view, his finest work might be the discovery and explanation of the so-called diffusion damping in solids: the Snoek effect, as described in a separate section. Snoek was a skilled experimentalist: not a great experimental virtuoso, who turned into quite new ways, but a person, who was able to choose effectively the methods to obtain results fast and reliably. His enormous power and the strong concentration—obsession almost—with which he engaged in a subject, is characteristic. Thereby he did not let himself be stopped by rejections and criticism of other people: his strength was that he tackled the problems in an original and unconventional way. If he might sometimes get on the wrong track, his perseverance and his physical intuition brought him at last to valuable results. Because of his obsessiveness he was not always an easy colleague, yet, just because of that, he often could throw a surprising light, also on problems of other persons; thus he inspired many people. In the spring of 1948 he carried out a slowly ripened decision; he emigrated to the United States of America, where he joined a private research laboratory, Horizons Ltd. His stay there was too short to perform great work; Dr. J.L. Snoek died in a car accident on the 3 December 1950. His age was 48.
M. Koiwa / Materials Science and Engineering A 370 (2004) 9–11
Acknowledgements The author wishes to thank Dr. C. Tuijn of University of Amsterdam, who found the two articles [1,2] and kindly prepared the English translations.
References [1] H.B.G. Casimir, N.T. v. N., XVII (1951) 1. [Journal of the Dutch Physical Society]. [2] G. van Nifterik, Technisch Weekblad, 22 May 1996.
[3] [4] [5] [6] [7] [8] [9] [10]
11
E. Woodruff, Phys. Rev. 16 (1903) 321. J. Snoek, Physica 6 (1939) 591. J. Snoek, Physica 8 (1941) 711. T.S. Kˆe, Phys. Rev. 74 (1948) 9. T.S. Kˆe, Phys. Rev. 74 (1948) 914. C.A. Wert, J. Appl. Phys. 21 (1950) 1196. L.J. Dijkstra, R.J. Sladek, Trans. Metal. Soc. AIME 197 (1953) 69. M. Koiwa, Philos. Mag. 24 (1971) 81, 107, 539, 799; M. Koiwa, Philos. Mag. 25 (1972) 701. [11] H. Numakura, M. Koiwa, J. Phys. IV 6 (1996) C8–97. [12] H. Numakura, M. Koiwa, in: A. Wolfenden, V.K. Kinra (Eds.), M3D III Mechanics and Mechanism of Material Damping, ASTM Standard Technical Publication 1304, American Society for Testing and Materials, West Conshohocke, PA, 1998, p. 383.