Studies in Magnetism and Superconductivity under Extreme Pressure

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1 Washington University in St. Louis Washington University Open Scholarship All Theses and Dissertations (ETDs) Studies in Magnetism and Superconductivity under Extreme Pressure Wenli Bi Washington University in St. Louis Follow this and additional works at: Recommended Citation Bi, Wenli, "Studies in Magnetism and Superconductivity under Extreme Pressure" (2011). All Theses and Dissertations (ETDs) This Dissertation is brought to you for free and open access by Washington University Open Scholarship. It has been accepted for inclusion in All Theses and Dissertations (ETDs) by an authorized administrator of Washington University Open Scholarship. For more information, please contact

4 4f 7 ) 4f 6 ).

11 Γ t 1/2 α σ 0

12 T max c T max c P T c T c α = Rws R mo Z 98. α c 3.2

13 T c T c

14 T s T sc T Curie E A E B E F I II III ρ =5.25 I II III

15 III

16 θ α = arctan(h/r) β α

23 0.07

25 200 μm

26 T c Tc T c T c T c

27 δ T c (4f 7, J = 7 2 ) 4f 4f 6,J=0), T c T c

30 ( ) [ ωd 1 T c =1.14 exp k B N(E F )V eff ω D k B N(E F ) ] V eff T c k m e k/η m k η T c 1 m k η dt c /dp

31 k η. k k k T c T c η T c T c T c

32 H ambient pressure superconductor high pressure superconductor He Li Be Na Mg K Rb Cs Fr Ca Sr 7 50 Ba 5 18 Ra Sc Y Ti Zr insert Hf La-Lu insert Rf Ac-Lr T c (K) T max c (K) P(GPa) V Nb Cr Mo 0.92 Ta W Ha Mn Tc 7.77 Re 1.4 Fe Ru 0.51 Co Ni Rh Pd Os Ir T max c (K) P(GPa) Cu Ag Zn Cd 0.56 B Al 1.14 Ga Pt Au Hg- Tl C Si Ge In Sn Pb N O F Ne P As Sb Bi S Se Te Cl Br I Ar Kr Xe Po At Rn La-fcc Ac Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Th Pa 1.4 U 0.8( ) 2.4( ) Np Pu Am Yb Lu Cm Bk Cf Es Fm Md No Lr T max c P T c T c T max c

33 α R ws /R mo R ws =(3V a /4π) 1 3 V a = V/N A V N A R mo [Xe]4f 7 6s 2 4f R mo 4f 7 2 α Z 98. α c =3.2

34 α = Rws R mo Z 98. α c 3.2

35 4f 7 4f 6 ) J = 7 2 J =0) 4f 14 4f 13 ) α

36 P (V )= 3 2 B 0 [ (V0 V ) 7 3 ( V0 V ) 5 ]{ ( B ) [ ( V0 V ) ]},

38 V 0 B 0 B 0 4f n+1 (5d 0 6s) 2 4f n (5d6s) 3 ) 4f 7 ) (4f 14 )

39 4%

40 Eu ++ Eu f ( J 7 2) divalent antiferromagnet pressure 6 4 f ( J 0) trivalent Van Vleck paramagnet 4f 7 (J = 7 2 ) 4f 7, J = 7 2 4f 6, J =0) 5f 6, J =0)

41 L III T c dt c = +18 dp T c T c T c

42 T c (K) Y Sc La Lu 10 5 Eu P(GPa)

43 T c dt c dp T c T c, T c

44 T c T c

45 T c T c 150 4f 7

46 Tc

47 2.5

48 200 EuFe As T S ρ C T (K) AF T SC T Curie χ (H//ab) χ (H//c) χ ac T N 0 0 AF 5 SC FM P (GPa) T sc T s T Curie

50 μm μm θ)

52 x

53 photoelectron Auger electron E F x-ray E B fluorescence photon E A E A E B E F I = I o e μx I 0 I μ III I 1 2 I II 3, 2

54 10 4 M Eu μ/ρ (cm 2 /g) 10 2 L 10 0 K photon energy (kev) I II III ρ =5.25 i > f > Γ i,f = 2π <f r ε i > 2 δ (E f E i ω) i,f ε ω l = ±1 I II III

55 Continuum K L I L II L III 2p 2/3 2p 1/2 2s 1s I II III III

56 norm. XANES (a.u.) Eu 2+ Eu f 7 4f energy(kev) III 2p 6 3/2 4f 7 5d 0 6s 2 2p 5 3/2 4f 7 5d 1 6s 2 2p 6 3/2 4f 6 5d 1 6s 2 2p 5 3/2 4f 6 5d 2 6s 2 μ ln (I/I 0 )

57 μ I f /I 0 I f μx 2.5 Δμx < 1.5 Δμ III μx 2.5 μ/ρ = ρ = x 12 μm Δμx < 1.5 Δμ/ρ = ( ) 11 μm μm μm μm μm 5 μm

60 %. 10 2

61 ±1) Δm = ±1 Δl = ±1

62 L III Spin up Spin down 5d E F 4f L III 62.5% 37.5% 62.5% 37.5% RCP LCP L II III

63 μ) μ + μ μ XMCD = μ + μ, μ XMCD ρ( ) ρ( ) M ρ( ) ρ( ) M μ XANES =(μ + + μ ) /2 II,III 2p 3d IV,V 3d 4f 1s 4p II,III 2p 5d 0.2% L II,III

64 L III 12 μm 1

66 γ γ E R E R = E2 γ 2Mc, E γ γ M c γ E R E R E γ

67 E R γ E R γ E D = ve γ /c v ω(n+ 1 /2) E R ω f f = exp [ { ( ) 2 ˆ 6E R 1 T kθ D 4 + θ D θ D /T 0 }] xdx e x 1

68 γ τ γ τγ Γ. σ 0 =2πλ 2 2I e I g +11+α I e I g α γ λ α γ E R ) γ γ f σ 0 E R t 1 2 t 1 2 τ ln 2

69 Γ t 1 2 Γ t 1 2 Γ α γ γ γ v γ E γ v/c

70 IS IS = C δr R Δρ e(0) C δr R Δρ e (0) δr R δr R δr R s s 1s, 2s 3s IS s H μ I 2I +1 E m = μhm I I = gμ N Hm I μ N = e /2Mc μ

71 g = μ/(iμ N ) m I = I, I 1, Δm I =0, ±1 V zz = 2 V/ z 2 E Q = eqv zz 4I(2I 1) [ 3m 2 I I(I +1) ] ( ) 1/2 1+ η2. 3 η η = V xx V yy V zz 0 η 1 I = 1 2 I = 3 2 m I = ± 3 2 m I = ± 1 2. Γ/E = 10

72 E 0 Γ t 1 2 α σ 0 ) Γ t 1/2 α σ

74 1

75 v γ E γ v/c E γ /c

76 μm

77 (a) (b) intensity (a.u.) IS = 2.0 mm/sec IS = 2.15 mm/sec IS = 2.15 mm/sec, QS = 0.5 mm/sec time (nsec) IS = 2.0 mm/sec IS = 2.15 mm/sec IS = 2.15 mm/sec, QS = 0.5 mm/sec velocity (mm/sec) 1 4

79 10 μm.

80 1 4 μm μm

81 P (bar) =1+ ( ) (V 1.002) ( )

82 6

83 0.6 19

84 3 μv 16 μv

85 0.02 ROCTEC 500 from Kennametal ROCTEC 500 from Kennametal 2.2 K moment (emu/g) cooling with 100 Oe Moment (emu/g) K RT T (K) Field (Oe) θ α β

86 θ β α θ α =arctan(h/r)

87 40 He pressure medium nonhydrostatic resistivity P (GPa) P (bar) 250 μm

88 300 μm 15 μm 5 μm

90 )

91 ν 0 (t) = t 3/ t t 5/ t 3, ν 0 (t) t = T 300(K) [ ( P (GP a) = 1876 ) λ 1], λ 0 λ 0

94 1

95 [ Δν P (GP a) K ( ) ] Δν K 0 1 ν 0 2 ν 0 ν 0 = 1333 ± 1 K 0 K 0

97 μm

98 T c T c

99 Oscillator (SR830) 700 Ohms Computer Lock in Amplifier (SR830) pre amp (SR554) secondary coils cryostat primary coils sample current source thermometer Pt, Ge digital volt meter S = πfαhv N R(1 D) χ. f : α 1/ 1+(L/R) 2 L : H : V : ) N : R : D : χ = 1

100 μm μm μm μm 40

101 120 In Sun's cell In our cell χ' (μv) T (K)

102 μm μm

103

104

105 μm μm μm ± μm 4 4

106 μm μm 3000

107

108

109

110

111

112 μm

113 20.0 mm primary coil secondary coil 6.2 mm 2.0 mm sample space

114

115

116 T c dt c dp

117

118

119

120

121 0 Enthalpy [mev/atom] (a) (b) (c) (d) (e) (c) (b) -300 (a) bcc Pressure [GPa] (b) hcp (c) C2/c (d) Fdd2 (e) Pnma

122 Enthalpy (mev/atom) bcc hcp Pnma (a) (b) (c) (d) Pressure (GPa) (a) (b) (c) (d)

123 3

124 8 6 (a) bcc (0GPa) hcp (15GPa) Phonon DOS (arbitrary units) (b) Pnma (90GPa) hcp (90GPa) Energy (mev)

125

126

127

128

129

130

131 6 bcc hcp orthorohmbic 1.7 hcp orthorohmbic lattice parameters ( ) 5 4 a c c a b Eu lattice parameter ratios c/a a/c b/c Eu a c 0 50 P (GPa) 100 (a) a/b P (GPa) 100 (b) 1.2

132 B o B o

133

134

135

136 +0.018

137

138 μm μm μm μm 0.82

139 L III μm μm μm μm 70 μm

140

141 1, μ μ L III μm μm L III

142 2 Eu normalized XANES (a. u.) GPa 5.0 GPa 8.4 GPa 21.6 GPa energy(kev)

143 15 μm μm μm

144 μm μm μm μm μm μm 100 μm μm 2 30 μm 2 μm μm μm

145 μm μm

146

147 μm μm μm μm μm 35 μm μm 20 μm

148

149

150 .

151 5d 1.0 (a) (b) d 4f d d Interstitial d 4f Pressure (GPa) f d Interstitial Pressure (GPa) 2.2 Interstitial 2.4 5d d (c) 4f + Interstitial 5d 4f + Interstitial Pressure (GPa) f + Interstitial XANES (a. u.) 1 0 (d) 3.8 GPa (bcc) 10.6 GPa (bcc) 12 GPa (hcp) 17 GPa (hcp) E-E F (ev) 0.14

152

153 4f density of states (a) 4 GPa 12 GPa 35 GPa 62 GPa 88 GPa 5d density of states (b) 10.6 GPa - bcc 12 GPa - hcp E - E F (ev) E - E F (ev) 5d density of states 0.4 (c) GPa 35 GPa 62 GPa 88 GPa 5d density of states (d) 35 GPa - hcp 37 GPa - Pnma E - E F (ev) E - E F (ev)

154

155 Eu XANES (a. u.) GPa 9 GPa 12 GPa 17 GPa 31 GPa 43 GPa 73 GPa energy (kev)

156 1 d 0.5 Electrons 0 s -0.5 p Pressure (GPa)

157 2.5 μm III μm μm μm

158 norm. XANES (a.u.) GPa 21.4 GPa XMCD amplitude * GPa 21.4 GPa energy(kev) energy(ev)

159

160

161 raw XMCD amplitude 4.0x x10 5 (b) 3.3 GPa 4.6 K 2 scans -8.0x magnetic field (T)

162 μm μm μm μm μm

163 θ ( ( )) arctan 1mm/2 2mm θ ( ) arctan( 1.6mm/2 ) 2mm

164

165 (a) P = 4.0 GPa (b) P = 9.0 GPa (c) P =14.0 GPa (d) P = 17.0 GPa (e) P = 25.0 GPa time (nsec) velocity (mm/sec)

166

167

168 (a) P = 12.0 GPa (b) P = 19.9 GPa (c) P = 24.0 GPa (d) P = 29.0 GPa (e) P = 35.6 GPa time (nsec) velocity (mm/sec)

169 (a) P = 23.1 GPa (b) P = 45.2 GPa (c) P = 52.4 GPa (d) P = 58.0 GPa (e) P = 65.5 GPa (f) P = 72.6 GPa time (nsec) velocity (mm/sec)

170

171 12 4f 7 4f 6 dis dp

172

173

174

175

176 x

177 x

178 χ ( emu/cm 3 ) 0.0 P(GPa) LaO 0.93 F 0.07 FeAs T(K)

179

180 2 T C (K) K/GPa (2) K/GPa , 11, 12, , 9 5 LaO 0.93 F 0.07 FeAs P(GPa) 0.07

181 LaO 0.86 F 0.14 FeAs χ (emu/cm 3 ) -0.1 P(GPa) T(K)

182

183 + )

184 13 12 K/GPa 0. 30(1) K/GPa 2 2' T C (K) ' 9' 8' 10' 6', 7' 6, 7 5' 4' 11' 3' ', 13' LaO 0.86 F 0.14 FeAs P(GPa) 0.14

185 0 0

186

187

188

189

190 4 EuFe 2 As 2 χ'(emu/mol) 2 T N P(GPa) T(K) 40 50

191 T c C

192

193 EuFe Co As χ'(emu/mol) P(GPa) T C T(K) 30 1

194

195 21 2 T (K) C,N (1) K/GPa 3 EuFe 2 As 1.4 P , 4 1' 0.35(3) K/GPa 2.0(1) K/GPa 4' 3 3' EuFe Co As 2 2' 2 EuFe 2 As 2 5' P(GPa)

196 μm μm 200 μm 70 μm 100 μm μm

197 60 χ' (nv) 6 EuFe 2 As 2 P = 0 GPa χ' (nv) T (K) T (K) μm

198

199 μm μm

200

201

202

203

204 T c 14

205 μm μm 2 T c μm

206

207

208

209

210

211

212

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