Ref. p. 105] 1.5.1 3d elements with Cu, Ag or Au: introductory remarks 1 1 Magnetic properties of 3d, 4d, and 5d elements, alloys and compounds 1.1 - 1.4 See Subvolume III/32A 1.5 Alloys and compounds of 3d elements with main group elements 1.5.1 3d elements with Cu, Ag or Au 1.5.1.1 Introduction General remarks In this subsection, experimental data for alloys with 3d transition elements (V, Cr, Mn, Fe, Co and Ni) and noble metals (Cu, Ag, Au) are compiled. These data were published in the period between 1983 and 1994. Data published before 1983 were filed in Landolt-Börnstein New Series, vol. III/19B edited by G. Zibold. Some data published in 1983 and 1984 were already referred by the previous editor. These data were omitted to avoid the duplication. For the compilation of data, we followed the policy of previous editor. Thus, amorphous systems, thin films, ultra-fine particles and precipitates, which are the fields growing very rapidly, are not treated in this subsection. The ordered alloys and ternary alloys are filed at the end of the subsection. The atomic short range order is referred only when it seems to have a significant relation with the magnetism of the alloys. 1.5.1.2 Definition of various kinds of magnetism 1.5.1.2.1 Spin glass, cluster glass, mictomagnetism and reentrant spin glass The most of data published in this period in the field of the subsection are concerned with spin glasses. Spin glass in a wide sense is usually used for the system with strong viscous magnetism below a characteristic temperature T (freezing temperature) but without any magnetic long range f order. In a narrow sense, it is used especially for the dilute alloys which can be approximately considered to have a random distribution of the magnetic components. Some authors use cluster glass or mictomagnetism for the system with higher concentration ( > few at% ) of magnetic component. Except for T, however, physical properties (the cusp shaped anomaly in the susceptibility, a broad f distribution of relaxation time and so on) are not sensitive to the concentration of the magnetic component. Reentrant spin glass also shows the viscous magnetism below the characteristic temperature T, f but above it, long range magnetic order (ferromagnetism or antiferromagnetism) is observed. Actual microscopic spin configurations of both high temperature phase and reentrant spin glass phase are still controversial. Many experimental results for spin glasses, together with the theories, are reviewed in [83f1, 85f1, 86b1, 88m1, 88m2, 91f1]. Landolt-Börnstein New Series III/32B 2 1.5.1 3d elements with Cu, Ag or Au: introductory remarks [Ref. p. 105 1.5.1.2.2 Diamagnetism Diamagnetism is known as a system which shows a negative susceptibility of the order of - 10- 5 to the applied magnetic field. The response is temperature independent. The origin of diamagnetism is an orbital motion of electrons around the nuclei, induced electromagnetically by the applied field. 1.5.1.2.3 Paramagnetism If the temperature is high enough to exceed the coupling energy between magnetic moments, the orientation of each moment rotates freely due to the thermal agitation. This is a paramagnetic state. The susceptibility of paramagnetism is an order of 10- 3…10- 6 and inversely proportional to the absolute temperature (K). Pauli paramagnetism comes from the excitation of conduction electrons in metallic system and shows a temperature independent susceptibility. Superparamagnetism is used for magnetic particles or clusters, inside of which magnetic order develops, but total ordered moment of each particle (cluster) rotates freely by thermal energy. An assembly of magnetic particles (clusters) with various particle sizes shows similar behaviors in the susceptibility to that of cluster glass. 1.5.1.2.4 Ferromagnetism In a ferromagnet a spontaneous magnetization exists, i.e., the magnetic moments are aligned parallel to one another without applied magnetic field. This is due to the positive exchange interaction between neighbouring spins. The spontaneous magnetization decreases with increasing temperature and becomes zero at the Curie temperature T . Above T it behaves as the paramagnet and the C C susceptibility obeys a Curie-Weiss law. 1.5.1.2.5 Antiferromagnetism In an antiferromagnet the magnetization is completely cancelled. The magnetic lattices are separated into sublattices. The magnetic moments in each sublattice are aligned parallel to one another but total magnetization is zero due to the cancellation of the magnetic moments between different sublattices. The susceptibility is small and positive. The susceptibility as a function of temperature shows a maximum at the ordering temperature (Néel temperature) T . N A period of magnetic order is not always commensurate with the lattice period. A spin density wave (SDW) has an incommensurate spin alignment with a wave vector which is determined by the Fermi surfaces of conduction electrons. 1.5.1.2.6 Ferrimagnetism In a ferrimagnet magnetizations between sublattices with antiparallel coupling are not cancelled and behave almost like the ferromagnet below the ordering temperature T . N 1.5.1.2.7 Metamagnetism Metamagnetism is a magnetically ordered state which shows zero magnetization under the zero magnetic field but abrupt increasing of magnetization at the certain magnetic field. The hysteresis for the change of magnetic field is small. Landolt-Börnstein New Series III/32B Ref. p. 105] 1.5.1 3d elements with Cu, Ag or Au: introductory remarks 3 1.5.1.3 Some remarks on magnetization 1.5.1.3.1 Spontaneous magnetization In a ferromagnet, magnetic moments coupling with the positive exchange interaction are aligned parallel to one another at temperature below T and the spontaneous magnetization results without C external magnetic field. 1.5.1.3.2 Saturation magnetization A bulk ferromagnet is divided into many ferromagnetic domains under zero magnetic field and total magnetization is far smaller than the spontaneous magnetization. The magnetization however reaches to the saturated value under rather weak applied field due to the realignment of magnetic domains. This is called a saturation magnetization. 1.5.1.3.3 Thermoremanent magnetization (TRM) A thermoremanent magnetization is observed when a spin glass sample is cooled down through T f under certain magnetic field, then the magnetization is measured after removing the magnetic field. 1.5.1.3.4 Isothermal remanent magnetization (IRM) An isothermal remanent magnetization is measured below T for the spin glass sample cooled down f under zero magnetic field. 1.5.1.3.5 Wait time effect in spin glass The spin glass has a strong magnetic viscousity and the relaxation time of the magnetization distributes continuously from atomic time scales to macroscopic time scales. A spin glass sample is cooled down from a reference temperature above T to the measurement temperature T (below T ) f m f in the zero magnetic field. At T the sample is kept at constant temperature for a certain wait time t m w before the external field is applied, then the time development of the IRM is measured in a constant magnetic field. The IRM shows a striking wait time dependence (Fig. 43). The same kind of wait time effect can be observed for the TRM. 1.5.1.3.6 Magnetic anisotropy In actual magnetic substances the internal energy depends on the direction of spontaneous magnetization. Generally the magnetic anisotropy is a reflection of crystal symmetry of the sample and is called a magnetocrystalline anisotropy. Another type of anisotropy is an induced magnetic anisotropy which is induced by some treatment such as field cooling, cold working or neutron irradiation. Anisotropy energy is usually expressed in the form of an anisotropy constant K times an angular dependence. An axial anisotropy has a p symmetry and an easy axis is parallel to one of crystal axes. Directional anisotropy is independent from crystal axes and has a 2p symmetry. The Dzyaloshinsky-Moriya interaction causes the directional anisotropy. Landolt-Börnstein New Series III/32B 4 1.5.1 3d elements with Cu, Ag or Au: introductory remarks [Ref. p. 105 1.5.1.4 Remarks on the data analysis 1.5.1.4.1 Curie-Weiss law The susceptibility of paramagnetic substance is described as m Np2 c (T)= 0 eff (1) 3k (T- Q ) B where N is number of magnetic atoms per unit mass, Q is the paramagnetic Curie temperature and p shows the effective magnetic moment. The effective moment and the paramagnetic Curie eff temperature are deduced by a plot of c –1(T) versus T as the slope of straight line and its intercept with abscissa, respectively. The effective moment is related to the total angular momentum J = L + S as p2 =g2J(J+1)m 2 (2) eff B with the Landé g-factor. 1.5.1.4.2 Arrott plot Above the Curie temperature, the magnetization for ferromagnetic substance approximately obeys the equation H T- T M ( )= C +( )2 (3) M T M 1 1 where M and T are constants. This is a result of the mean field approximation. Arrott plots are 1 1 isotherm of H/M versus M2 plot and parallel straight lines are obtained for each temperature. The Curie temperature T is determined by the straight line which passes through the origin. C 1.5.1.5 High frequency properties The time development of spin configuration is a fundamental aspect to understand the microscopic picture of the spin glasses. Since various experimental techniques have each characteristic frequency, experimental data obtained by different techniques give us the information of the system in different time scale. 1.5.1.5.1 Neutron scattering The characteristic frequency of neutron diffraction is typically about 10- 10(cid:1)10- 11 s. The fastest motion of spins is measurable as inelastic scattering of neutrons (Fig. 21). The spin dynamics slower than this time scale is observed as elastic scattering (Fig. 20). The freezing temperature of spin glass studied by neutron elastic scattering is always higher than that determined from the cusp in the susceptibility or the disappearance of hyperfine field in Mössbauer spectroscopy (Fig. 32). 1.5.1.5.2 NMR and Mössbauer spectroscopy (ME) Both techniques enable the measurement of the hyperfine magnetic field at the nuclear position. In spin glass system, the finite value of hyperfine field is usually observed below T. The lifetime of the f Landolt-Börnstein New Series III/32B Ref. p. 105] 1.5.1 3d elements with Cu, Ag or Au: introductory remarks 5 excited nuclear level in typical ME absorber Fe57 is 1(cid:215)10- 7 s. The spin dynamics faster than this time scale is observed as a paramagnetic component [85M3]. For ferromagnetic substances, the NMR signal is enhanced by the displacement of domain walls driven by the external rf-field. 1.5.1.5.3 mmmm SR In the muon spin relaxation technique, the polarized muons with positive charge are shot into the sample. When the muon, which is trapped at the interstitial site of the sample, decays into positron after a lifetime of 2.2 m s, the information of local magnetic field is recorded as a depolarization of the muon spin. Thus the characteristic frequency of m SR is 10- 6 s. With this technique, the transition to the spin glass phase and dynamics in this phase can be studied (Figs. 69-78). 1.5.1.5.4 ESR ESR probes the local magnetic moment through the magnetization of conduction electrons. In spin glasses, remarkable increases of the linewidth W and the resonance shift d H are observed around T res f and these enlargements are frequency dependent (Fig. 140). 1.5.1.5.5 Perturbed angular correlation (PAC) PAC spectroscopy observes the hyperfine field through the nuclear spin precession in the time scale determined by the lifetime of the probe (» 10- 7…10- 8 s). After the emission of first g -ray, nuclear spin in the intermediate state interacts with an electromagnetic field and precesses, causing the angular correlation of the second g -ray emission to change. From PAC spectroscopy data, the temperature dependence of hyperfine field and the distribution of local magnetic field in spin glasses are discussed (Fig. 59). 1.5.1.6 Hall resistivity Hall resistivity in noble metal with dilute magnetic impurities is expressed as r H = R0B + RHM (4) where B and M indicate the magnetic induction and the magnetization, respectively. The first term is an ordinary Hall effect and is associate with the Lorentz force for noble metals. The second term is called the extraordinary or anomalous Hall resistivity and shows the orbital contribution to the local impurity moments. The anomalous Hall coefficient (R ) which includes the information about the H orbital susceptibility is compared with the susceptibility data for spin glasses (Fig. 209). 1.5.1.7 Remarks on some concepts of metallurgy Magnetic properties of alloys depend not only on the concentration of magnetic atoms but also on their spacial arragement. In an ideal spin glass, a random distribution of magnetic atoms is assumed. Most of spin glass theories are based on this assumption but in actual substances, it is difficult to produce random alloys. The spacial distribution of magnetic atoms in alloys can be partly controlled by the appropriate thermal treatment. Landolt-Börnstein New Series III/32B Ref. p. 105] 1.5.1 3d elements with Cu, Ag or Au: introductory remarks 5 excited nuclear level in typical ME absorber Fe57 is 1(cid:215)10- 7 s. The spin dynamics faster than this time scale is observed as a paramagnetic component [85M3]. For ferromagnetic substances, the NMR signal is enhanced by the displacement of domain walls driven by the external rf-field. 1.5.1.5.3 mmmm SR In the muon spin relaxation technique, the polarized muons with positive charge are shot into the sample. When the muon, which is trapped at the interstitial site of the sample, decays into positron after a lifetime of 2.2 m s, the information of local magnetic field is recorded as a depolarization of the muon spin. Thus the characteristic frequency of m SR is 10- 6 s. With this technique, the transition to the spin glass phase and dynamics in this phase can be studied (Figs. 69-78). 1.5.1.5.4 ESR ESR probes the local magnetic moment through the magnetization of conduction electrons. In spin glasses, remarkable increases of the linewidth W and the resonance shift d H are observed around T res f and these enlargements are frequency dependent (Fig. 140). 1.5.1.5.5 Perturbed angular correlation (PAC) PAC spectroscopy observes the hyperfine field through the nuclear spin precession in the time scale determined by the lifetime of the probe (» 10- 7…10- 8 s). After the emission of first g -ray, nuclear spin in the intermediate state interacts with an electromagnetic field and precesses, causing the angular correlation of the second g -ray emission to change. From PAC spectroscopy data, the temperature dependence of hyperfine field and the distribution of local magnetic field in spin glasses are discussed (Fig. 59). 1.5.1.6 Hall resistivity Hall resistivity in noble metal with dilute magnetic impurities is expressed as r H = R0B + RHM (4) where B and M indicate the magnetic induction and the magnetization, respectively. The first term is an ordinary Hall effect and is associate with the Lorentz force for noble metals. The second term is called the extraordinary or anomalous Hall resistivity and shows the orbital contribution to the local impurity moments. The anomalous Hall coefficient (R ) which includes the information about the H orbital susceptibility is compared with the susceptibility data for spin glasses (Fig. 209). 1.5.1.7 Remarks on some concepts of metallurgy Magnetic properties of alloys depend not only on the concentration of magnetic atoms but also on their spacial arragement. In an ideal spin glass, a random distribution of magnetic atoms is assumed. Most of spin glass theories are based on this assumption but in actual substances, it is difficult to produce random alloys. The spacial distribution of magnetic atoms in alloys can be partly controlled by the appropriate thermal treatment. Landolt-Börnstein New Series III/32B 6 1.5.1 3d elements with Cu, Ag or Au: introductory remarks [Ref. p. 105 1.5.1.7.1 Quenching The structural characteristic at high temperature can be more or less retained by cooling the sample very rapidly (quenching). If the measurement temperature is not high enough for atoms to diffuse in the sample, quenched state would be retained as an unstable state. An atomic diffusion constant, however, is function of temperature, density of defects, atomic sizes, and so on, and these values vary from systems to systems. It depends on the alloy systems whether the rapid quenching is effective or not. 1.5.1.7.2 Annealing, ageing Heating a sample to high temperature and keeping it for a certain period in order to promote an atomic diffusion is reffered to as annealing. Annealing is carried out for various purposes; to homogenize the composition, to grow the precipitates or the atomic short range order, to relax the strain introduced by the treatment on preparing the specimen. Ageing corresponds to annealing at comparatively low temperature and for long period. 1.5.1.7.3 Cold working, plastic deformation Cold working or plastic deformation deforms the shape of the sample macroscopically and introduce many atomic defects and dislocations. These are considered to cause decreases in the average magnetic moment and the atomic short range order. Landolt-Börnstein New Series III/32B Ref. p. 105] 1.5.1.8 Survey 3d elements with Cu 7 1.5.1.8 Surveys Survey 1. Binary 3d- Cu alloys. Numbers in italic and roman refer to tables and figures, respectively. For ternary alloys containg Cu, see Survey 4. Alloy Mn- Cu Fe- Cu Co- Cu Ni- Cu Magnetic structure 15-20, 22 Magnetic phase diagram 11-14 104, 105 114 Transition temperature Magnetic susceptibility 7, 106, 107 118 Critical exponent 3 Paramagnetic properties Curie-Weiss law 24 p 4 eff Q 4 Spin-glass, and mictomagnetic properties susceptibility 9, 23, 25-31, 42, 115 71, 74 T 1, 2 105 9 f M, IRM, TRM, M(t) 34-41, 43, 47-50 116 magnetic cluster 33 hysteresis 44, 86 anisotropy 45, 46, 52 109, 110 Ferromagnetic properties T 9 C M, M 0 Arrott plot hysteresis anisotropy Antiferromagnetic properties T N susceptibility 23 High-frequency properties neutron scattering 5, 21, 32, 33, 71, 73 10, 117 NMR 2, 53-58 Mössbauer 111 m SR 69-78 PAC 59 7 ESR 10, 60-68 Transport properties 87-97 113 120 Magneto-mechanical properties 79 Heat properties 51, 80-86 Landolt-Börnstein New Series III/32B 8 1.5.1.8 Survey 3d elements with Ag [Ref. p. 105 Survey 2. Binary 3d- Ag alloys. Numbers in italic and roman refer to tables and figures, respectively. For ternary alloys containg Ag, see Survey 4. Alloy Mn- Ag Fe- Ag Magnetic structure 22, 125 Magnetic phase diagram 6, 124 Transition temperature Magnetic susceptibility Critical exponent 3 7 Paramagnetic properties Curie-Weiss law 11, 126 p 11 eff Q 11 Spin-glass and mictomagnetic properties susceptibility 8 ,9, 127, 128 T 1, 1 f M, IRM, TRM, M(t) 129-133 magnetic cluster hysteresis anisotropy 134 Ferromagnetic properties T C M, M 0 Arrott plot hysteresis anisotropy Antiferromagnetic properties T N susceptibility High-frequency properties neutron scattering NMR 2, 135 Mössbauer m SR 142, 143 PAC 7 ESR 10, 136-141 Transport properties 144 Magneto-mechanical properties Heat properties Landolt-Börnstein New Series III/32B Ref. p. 105] 1.5.1.8 Survey 3d elements with Au 9 Survey 3. Binary 3d- Au alloys. Numbers in italic and roman refer to tables and figures, respectively. For ternary alloys containg Au, see Survey 4. Alloy V- Au Cr- Au Mn- Au MnAu Mn Au 4 2 5 Magnetic structure Magnetic phase diagram 148 Transition temperature Magnetic susceptibility 146 Critical exponent Paramagnetic properties Curie-Weiss law p 145 13 eff Q 13 Spin-glass and mictomagnetic properties susceptibility 152 T 1, 13, 2 f M, IRM, TRM, M(t) 149 153 magnetic cluster hysteresis anisotropy Ferromagnetic properties T 14 C M, M 0 Arrott plot hysteresis anisotropy Antiferromagnetic properties T 14 N susceptibility High-frequency properties neutron scattering 73 NMR 2 Mössbauer m SR 73, 76, 78 PAC ESR Transport properties 147 154-156 Magneto-mechanical properties 14 14 Heat properties 14, 157 14, 157 Landolt-Börnstein New Series III/32B