Fe Co Si. Fe Co Si. Ref. p. 59] d elements and C, Si, Ge, Sn or Pb Alloys and compounds with Ge

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1 Ref. p. 59] d elements and C, Si, Ge, Sn or Pb Co Si Co Si H cr Magnetic field H [koe] C C IF "A" P Frequency ωγ / e [koe] Fig Co 0. Si. Magnetic phase diagram in a magnetic field vs. temperature plane, as determined from magnetic measurements on a single crystal with the magnetic field H along the [1] direction. The compound has a helical spin structure for H = 0. C: conical arrangement of the spins; IF: field-induced ferromagnetism; P: paramagnetism; "A": unknown spin structure with a dip of magnetization. The chain line within the C region indicates a reorientation of the propagation vector of the cone-type magnetic structure to the direction of the applied magnetic field, when it is not along the field initially [90I1] Applied field [koe] H appl Fig Co 0. Si. ESR frequency ω/γ e at. K plotted against the magnetic field applied, H appl, along the [001] axis of a single crystal. H cr is the critical field for induced ferromagnetic spin structure. The broken curve shows the theoretical curve for a helical spin resonance based on the antisymmetric exchange interaction of the Dzyaloshinski-Moriya type. The frequency is expressed in terms of ω/γ e, the angular frequency divided by the magnetomechanical ratio of a free electron [89W1] Alloys and compounds with Ge The existence of two successive magnetic transitions in Ge has been established by [85C1] and the proposed collinear spin structure at lower temperature range seems to be supported theoretically [91G1], but it is still the subject of active discussion, because neither the anisotropy of magnetic susceptibility nor the magnetization curves in strong magnetic fields are consistent with the collinear spin structure [89Z1]. For the related ternary compound 1 x Co x Ge it is claimed [88P1] that crystal defects increase in the single-crystal specimens as x increases. This may lead to another complication for the physical properties of these compounds. In the series of ternary compounds 3 x V x Ge, doubly ordered cubic, L 1 (Heusler alloy) type of crystal structure has been established through pulsed neutron powder diffraction at room temperature for x = 0., 0.8 and 1.0. The latter compound contains a small amount of undetermined second phase [90B1]. Survey Composition x Properties Figure Table α 1 x Ge x H hyp (x) at 9 Ge 93 γ( 0.7 Mn 0.3 ) 1 x Ge x χ(t;x), (x) 9, 95 3 Ge a, c, H hyp, E Q, IS 9 New Series III/3C

2 d elements and C, Si, Ge, Sn or Pb [Ref. p. 59 Composition x Properties Figure Table 5 Ge 3 α(t) 9 Ge (hex B35) T-H magnetic phase diagram 97 9 Ge (cub B0) I ND (T), I ND (H) 98, x Mn x Ge χ g (T), χ 1 g ( T) (x), Θ(x) 1 Ge Cp ( T) 9 I ND (T), Q(T) 3, 1 x Co x Ge χ g (T;x) 5 x-t magnetic phase diagram Table 9. Supplement to Table in LB III/19C, subsect Magnetic and related properties of 3 Ge [85H1], hexagonal [88B1] and cubic [89L1] Ge, and Ge [87D1]. 3 Ge 1 ) Ge 3 ) Ge T > 700 C metastable at T < 0 C [7R1] 0 C < T < 70 C [7R1] Crystal structure hexagonal hexagonal cubic tetragonal D0 19 (Ni 3 Sn) B35 (CoSn) B0 (Si) C1 (CuAl ) a [Å] c [Å] Magnetism ferro antiferro helical antiferro [K] 78.7 (first order) 90 p [µ B /] 1.38 structure 0 K < T< : long-range spiral first-order transition H hyp ( 57 ) [koe] E Q ( 57 ) [mm s 1 ] IS ( 57 ) [mm s 1 ] 0 at K 0.0 at K 0.39 ) at K collinear, p c 30 K < T < 0 K: double cone, cone axis c T < 30 K: similar to T > 30 K but with fieldinduced transitions by H c (λ Å) transition at : (down) = 11 K (up) = 5 K < T < : Q = Å 1 <0> T < : Q = Å 1 <111> at = 3 K < T < : p c, incommensurate spiral Q <0> T < : collinear p c 1 ) No new data are available for low-temperature cubic 3 Ge and for ferromagnetism of hexagonal 3 Ge. ) Relative to natural iron at RT. 3 ) No new data are available for monoclinic Ge stable at HT. New Series III/3C

3 Ref. p. 59] d elements and C, Si, Ge, Sn or Pb 9 80 Ge 1-x x 5 ( 0.7 Mn0.3) 1-x Gex 7 0 Hyperfine field H hyp [koe] H 3 H H Ge content x Fig. 93. Dilute 1 x Ge x (α phase). Hyperfine field H hyp at 9 Ge atom plotted against the Ge concentration. The hyperfine fields were determined by analyzing the data obtained by the time-differential perturbed angular distribution technique using the Ge isomer excited in heavy-ion reactions, and assigned as the contributions H i to the conduction-electron polarization from the first three (i = 1,,3) nearest neighbours [91L1]. Susceptibility (cgs) χ V [ ] x = Fig. 9. ( 0.7 Mn 0.3 ) 1 x Ge x (γ phase). Temperature dependence of the magnetic volume susceptibility χ V, measured in a magnetic field of koe for various Ge concentrations [90Z1]. The compositions are nominal and a small amount (< at%) of C is present. 0 0 ( 0.7 Mn0.3) 1-x Gex 0 35 Ge 5 3 Néel temperature [K] Expansion α [ K ] T C Mn Ge content x Fig. 95. ( 0.7 Mn 0.3 ) 1 x Ge x (γ phase). Dependence of the Néel temperature on the Ge concentration [90Z1], derived from the data of Fig Fig Ge 3, single crystal. Temperature dependence of the thermal expansion coefficient α. Solid circles: along a axis; open circles: along c axis [91M1]. New Series III/3C

4 d elements and C, Si, Ge, Sn or Pb [Ref. p. 59 Intensity I [ 3 counts ( min ) 1 ] Ge (cub) Fig. 98. Ge (cubic, B0 type). Temperature dependence, for decreasing temperature, of the neutron integrated intensity I of the satellite lines around the (000), specifying the propagation vector of longrange helical arrangement of spins. (1): Q 0 [0] where Q 0 = Å 1 ; (): sum of ( Q 0 / 3)( 111) and ( Q 0 / 3)( 111) where Q 0 = Å 1. The transition at the Néel temperature is inferred to be of first order with very little hysteresis, while the transition at with the change in the propagation vector shows pronounced hysteresis [89L1] Ge (cub) Magnetic field H ( c) [koe] T Ge (hex) C3 C C Fig. 97. Ge (hexagonal, B35 type). Magnetic phase diagram in a temperature - magnetic field plane, as determined by neutron diffraction in magnetic fields applied perpendicular to the c axis [88B1]. AF: collinear antiferromagnetic along c axis; C0, C1, C, C3: double cone antiferromagnetics with the axis of the cones along the c axis. The cone angle increases with decreasing temperature or increasing field. Transition between two C phases are characterized by a kink in the temperature dependence of the cone angle. (1) and (): field-induced transitions detected in experiments with the applied fields along reciprocal-lattice vectors [0] and [ ], respectively; (3): transitions observed in earlier study [8B1]. Antiferromagnetic basal-plane moment appears above the dotted curve. CO 1 3 AF Intensity I (relative ) Magnetic field H [Oe] Susceptibility g [ cm g ].5 5 Mn Ge Q 1 3 Inv. susceptibility g [ g cm ] Fig. 99. Ge (cubic, B0 type). Dependence at 50 K of the integrated intensity of specific satellites around (000) on the magnetic field along the [011] direction. (1): ± Q 0 (0); (): ± ( Q 0 / ) (011) appearing in the field direction above 80 Oe. Q 0 = Å 1 [89L1] Fig Mn Ge.1. Temperature dependence of the magnetic mass susceptibility χ g and of its inverse, χ g 1 [9H1]. New Series III/3C

5 I Ref. p. 59] d elements and C, Si, Ge, Sn or Pb Mn Ge 7-x x 15 Ge Temperature, Q [K] mag 1 1 Heat capacity C p [J mol K ] Q Mn content x Fig x Mn x Ge. Composition dependence of the Néel temperature and of the paramagnetic Curie temperature Θ [9H1] Fig.. Ge. Temperature dependence of the magnetic contribution to the specific heat at constant pressure, C p mag [85C1]. 1 Intensity I [ counts (30 s) ] 8 1 [ counts (30 s) ] Ge T [K] Fig. 3. Ge. Temperature dependence of the neutron diffraction intensity I of the (0) magnetic reflection. Inset shows a thermal hysteresis of about 0.5 K [87D1]. Modulation wavevector Qa / π Ge Fig.. Ge. Temperature dependence of the magnitude of the propagation vector Q representing the incommensurate modulation of spin arrangement. Q <0> [87D1]. New Series III/3C

6 d elements and C, Si, Ge, Sn or Pb [Ref. p Co Ge 1-x x 3 1 Susceptibility χ g [ cm g ] T x T T x x TN x= Fig x Co x Ge. Temperature dependence of the magnetic mass susceptibility χ g in a magnetic field of koe. : Néel temperature; : transition temperature to modulated spin structure; T x : transition temperature of unknown origin [93S3]. Temperature [K] TTtr AF I AF II Co Ge 1-x x Ge Co content x T x T x P * AF III two phases Fig.. 1 x Co x Ge. Magnetic phase diagram in a composition - temperature plane, as obtained from magnetic measurements. AF I: antiferromagnet with modulated spin structure; AF II: with collinear structure; AF III: unknown structure. Magnetization curves of polycrystal specimens are linear below T x * and above [93S3] Alloys and compounds with Sn Magnetic structure of Sn has been re-investigated. Unfortunately, the single crystal specimen is very difficult to obtain, because Sn is formed through a peritectic reaction of Sn and a Sn-rich liquid. The neutron-diffraction analysis has to be performed using powder specimens, leading to some ambiguity in the proposed magnetic structure. New Series III/3C