Washington University in St. Louis Washington University Open Scholarship All Theses and Dissertations (ETDs) 1-1-2011 Studies in Magnetism and Superconductivity under Extreme Pressure Wenli Bi Washington University in St. Louis Follow this and additional works at: http://openscholarship.wustl.edu/etd Recommended Citation Bi, Wenli, "Studies in Magnetism and Superconductivity under Extreme Pressure" (2011). All Theses and Dissertations (ETDs). 554. http://openscholarship.wustl.edu/etd/554 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 digital@wumail.wustl.edu.
4f 7 ) 4f 6 ).
0.86 0.14
Γ t 1/2 α σ 0
T max c T max c P T c T c α = Rws R mo Z 98. α c 3.2
T c T c
T s T sc T Curie E A E B E F I II III ρ =5.25 I II III
III
θ α = arctan(h/r) β α
0.07
0.07 0.14 0.14
200 μm
T c Tc T c T c T c
δ T c (4f 7, J = 7 2 ) 4f 4f 6,J=0), T c T c
( ) [ 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
k η. k k k T c T c η T c T c T c
H ambient pressure superconductor high pressure superconductor He Li Be 0.0004 0.026 14 30 Na Mg K Rb Cs 1.3 12 Fr Ca 25 161 Sr 7 50 Ba 5 18 Ra Sc 19.6 106 Y 19.5 115 Ti 0.39 3.35 56.0 Zr 0.546 11 30 insert Hf La-Lu 0.12 8.6 62 insert Rf Ac-Lr T c (K) T max c (K) P(GPa) V 5.38 16.5 120 Nb 9.50 9.9 10 Cr Mo 0.92 Ta W 4.483 4.5 43 Ha 0.012 Mn Tc 7.77 Re 1.4 Fe 2.1 21 Ru 0.51 Co Ni Rh Pd.00033 Os Ir 0.655 0.14 T max c (K) P(GPa) Cu Ag Zn 0.875 Cd 0.56 B 11 250 Al 1.14 Ga 1.091 7 1.4 Pt Au Hg- Tl 4.153 2.39 C Si 8.2 15.2 Ge 5.35 11.5 In Sn 3.404 3.722 5.3 11.3 Pb 7.193 N O F Ne P 13 30 As 2.4 32 Sb 3.9 25 Bi 8.5 9.1 0.6 100 S 17.3 190 Se 8 150 Te 7.5 35 Cl Br 1.4 100 I 1.2 25 Ar Kr Xe Po At Rn La-fcc 6.00 13 15 Ac Ce 1.7 5 Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Th 1.368 Pa 1.4 U 0.8( ) 2.4( ) 1.2 2.7 142 Np Pu Am 0.79 2.2 6 Yb Lu 12.3 174 Cm Bk Cf Es Fm Md No Lr T max c P T c T c T max c
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
α = Rws R mo Z 98. α c 3.2
4f 7 4f 6 ) J = 7 2 J =0) 4f 14 4f 13 ) α
P (V )= 3 2 B 0 [ (V0 V ) 7 3 ( V0 V ) 5 ]{ 3 1+ 3 ( B 0 4 4 ) [ ( V0 V ) 2 3 1 ]},
V 0 B 0 B 0 4f n+1 (5d 0 6s) 2 4f n (5d6s) 3 ) 4f 7 ) (4f 14 )
4%
Eu ++ Eu +++ 7 4 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)
L III T c dt c = +18 dp T c T c T c
T c (K) 20 15 Y Sc La Lu 10 5 Eu 0 0 50 100 150 P(GPa)
T c dt c dp T c T c, T c
T c T c
T c T c 150 4f 7
Tc
2.5
200 EuFe As 2 2 150 T S ρ C T (K) 100 50 AF T SC T Curie χ (H//ab) χ (H//c) χ ac T N 0 0 AF 5 SC FM 10 15 P (GPa) 20 25 T sc T s T Curie
0.4 30 μm μm θ)
x
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
10 4 M Eu μ/ρ (cm 2 /g) 10 2 L 10 0 K 10-2 10 0 10 1 10 2 10 3 10 4 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
Continuum K L I L II L III 2p 2/3 2p 1/2 2s 1s I II III III
norm. XANES (a.u.) 4 3 2 Eu 2+ Eu 3+ 1 0 4f 7 4f 6 6.94 6.96 6.98 7.00 7.02 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 )
μ I f /I 0 I f μx 2.5 Δμx < 1.5 Δμ III μx 2.5 μ/ρ = 412.7 ρ = x 12 μm Δμx < 1.5 Δμ/ρ = (412.7 152.2) 11 μm μm μm μm μm 5 μm
1 4 6 10 4 17%. 10 2
±1) Δm = ±1 Δl = ±1
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
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
L III 12 μm 1
γ γ E R E R = E2 γ 2Mc, E γ γ M c γ E R E R E γ
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
γ τ γ τγ Γ. σ 0 =2πλ 2 2I e +1 1 2I 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
Γ t 1 2 Γ t 1 2 Γ α γ γ γ v γ E γ v/c
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
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
E 0 Γ t 1 2 α σ 0 ) Γ t 1/2 α σ 0 7 2 5 2
1
v γ E γ v/c E γ /c
μm
10-5 10-6 (a) (b) intensity (a.u.) 10-7 10-8 10-9 10-10 IS = 2.0 mm/sec IS = 2.15 mm/sec IS = 2.15 mm/sec, QS = 0.5 mm/sec 10-11 0 50 100 time (nsec) IS = 2.0 mm/sec IS = 2.15 mm/sec IS = 2.15 mm/sec, QS = 0.5 mm/sec -10 0 10 velocity (mm/sec) 1 4
10 μm.
1 4 μm μm
P (bar) =1+ (3000 14.5) (V 1.002). 14.5 (11 1.002)
6
0.6 19
3 μv 16 μv
0.02 ROCTEC 500 from Kennametal ROCTEC 500 from Kennametal 2.2 K moment (emu/g) 0.006 cooling with 100 Oe Moment (emu/g) 0.01 0.00 50 K RT 0.004-0.01 0 100 200 300 T (K) -20000-10000 0 10000 20000 Field (Oe) θ α β
θ 31 0.4 β α θ α =arctan(h/r)
40 He pressure medium nonhydrostatic resistivity P (GPa) 20 0 0 20 40 60 P (bar) 250 μm
300 μm 15 μm 5 μm 1 9 1 3 1 3 1 2
)
ν 0 (t) = 14422.0 36.612t 3/2 + 169.77t 2 264.54t 5/4 + 112.54t 3, ν 0 (t) t = T 300(K) [ ( P (GP a) = 1876 ) 10.71 λ 1], 10.71 λ 0 λ 0
1
[ Δν P (GP a) K 0 1+ 1 ( ) ] Δν K 0 1 ν 0 2 ν 0 ν 0 = 1333 ± 1 K 0 K 0
μm
T c T c
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
μm μm 40 95 μm μm 40
120 In Sun's cell In our cell χ' (μv) 60 0 0 100 200 300 T (K)
μm μm
μm μm μm ± μm 4 4
μm μm 3000
μm
20.0 mm primary coil secondary coil 6.2 mm 2.0 mm sample space
T c dt c dp
0 Enthalpy [mev/atom] -100-200 (a) (b) (c) (d) (e) (c) (b) -300 (a) bcc 0 20 40 60 80 100 Pressure [GPa] (b) hcp (c) C2/c (d) Fdd2 (e) Pnma
Enthalpy (mev/atom) 0-100 -200 bcc hcp Pnma (a) (b) (c) (d) -300 0 20 40 60 80 100 Pressure (GPa) (a) (b) (c) (d)
3
8 6 (a) bcc (0GPa) hcp (15GPa) Phonon DOS (arbitrary units) 4 2 0 4 3 (b) Pnma (90GPa) hcp (90GPa) 2 1 0 0 5 10 15 20 25 30 35 Energy (mev)
6 bcc hcp orthorohmbic 1.7 hcp orthorohmbic lattice parameters ( ) 5 4 a c c a b Eu lattice parameter ratios 1.6 1.5 c/a a/c b/c Eu 2.0 1.6 3 a c 0 50 P (GPa) 100 (a) a/b 1.4 0 50 P (GPa) 100 (b) 1.2
B o B o
+0.018
μm μm μm μm 0.82
L III μm μm μm μm 70 μm
1, μ μ L III μm μm L III
2 Eu normalized XANES (a. u.) 1 0 0.2 GPa 5.0 GPa 8.4 GPa 21.6 GPa 6.94 6.96 6.98 7.00 energy(kev)
15 μm μm μm
μm μm μm μm 20 30 μm μm 100 μm μm 2 30 μm 2 μm μm μm
μm μm
μm μm μm μm μm 35 μm μm 20 μm
.
5d 1.0 (a) 6.60 1.0 (b) 1.6 0.8 0.6 5d 4f 6.64 6.68 5d 0.8 0.6 5d Interstitial 1.8 2.0 0.4 0.2 5d 4f 0 20 40 60 80 Pressure (GPa) 6.72 6.76 4f 0.4 0.2 5d Interstitial 0 20 40 60 80 Pressure (GPa) 2.2 Interstitial 2.4 5d 0.92 0.69 0.46 0.23 5d (c) 4f + Interstitial 5d 4f + Interstitial 0 20 40 60 80 Pressure (GPa) 8.4 8.6 8.8 9.0 9.2 4f + Interstitial XANES (a. u.) 1 0 (d) 3.8 GPa (bcc) 10.6 GPa (bcc) 12 GPa (hcp) 17 GPa (hcp) 0 20 40 E-E F (ev) 0.14
4f density of states 20 10 0-10 (a) 4 GPa 12 GPa 35 GPa 62 GPa 88 GPa 5d density of states 0.8 0.4 0.0-0.4 (b) 10.6 GPa - bcc 12 GPa - hcp -20-2 0 2 4 E - E F (ev) -0.8-5 0 5 10 15 20 E - E F (ev) 5d density of states 0.4 (c) 0.2 0.0-0.2 12 GPa 35 GPa 62 GPa 88 GPa 5d density of states 0.4 0.2 0.0-0.2 (d) 35 GPa - hcp 37 GPa - Pnma -0.4 0 10 20 E - E F (ev) -0.4 0 10 20 E - E F (ev)
Eu XANES (a. u.) 1 0.6 GPa 9 GPa 12 GPa 17 GPa 31 GPa 43 GPa 73 GPa 0 6.98 7.00 7.02 energy (kev)
1 d 0.5 Electrons 0 s -0.5 p 0 10 20 30 40 50 60 70 Pressure (GPa)
2.5 μm III μm μm μm
norm. XANES (a.u.) 2 1 3.3 GPa 21.4 GPa XMCD amplitude *100 4 3 2 1 3.3 GPa 21.4 GPa 0 6.94 6.96 6.98 7.00 energy(kev) 0 6.94 6.95 6.96 6.97 6.98 6.99 7.00 energy(ev)
raw XMCD amplitude 4.0x10 5 0.0-4.0x10 5 (b) 3.3 GPa 4.6 K 2 scans -8.0x10 5-4 -2 0 2 4 magnetic field (T)
μm μm μm μm μm
θ ( ( )) arctan 1mm/2 2mm θ ( ) arctan( 1.6mm/2 ) 2mm
10 4 10 3 10 2 10 1 10 0 10 4 (a) P = 4.0 GPa (b) P = 9.0 GPa 10 3 10 2 10 1 10 4 10 3 10 2 10 1 10 0 10 4 10 3 10 2 10 1 10 4 10 3 (c) P =14.0 GPa (d) P = 17.0 GPa (e) P = 25.0 GPa 10 2 10 1 20 40 60 80 time (nsec) -10 0 10 velocity (mm/sec)
10 5 10 4 (a) P = 12.0 GPa 10 3 10 2 10 3 (b) P = 19.9 GPa 10 2 10 1 10 4 10 3 (c) P = 24.0 GPa 10 2 10 1 10 4 10 3 10 2 10 1 10 5 10 4 (d) P = 29.0 GPa (e) P = 35.6 GPa 10 3 10 2 20 40 60 80 time (nsec) -10 0 velocity (mm/sec)
10 4 10 3 10 2 10 1 10 3 (a) P = 23.1 GPa (b) P = 45.2 GPa 10 2 10 1 10 4 10 3 10 2 10 1 10 3 (c) P = 52.4 GPa (d) P = 58.0 GPa 10 2 10 1 10 4 10 3 (e) P = 65.5 GPa 10 2 10 1 10 4 10 3 10 2 10 1 (f) P = 72.6 GPa 20 40 60 80 time (nsec) -10 0 velocity (mm/sec)
12 4f 7 4f 6 dis dp
x
x
χ ( emu/cm 3 ) 0.0 P(GPa) 0 0.40 0.58 0.78-0.1 LaO 0.93 F 0.07 FeAs 18 20 T(K) 22 24 0.07
3 3 4 4 5
2 T C (K) 22.0 + 2 K/GPa 4 13 3 7 21.5 + 1.20 (2) K/GPa 21.0 1 6, 11, 12, 14 10 8, 9 5 LaO 0.93 F 0.07 FeAs 0.0 0.5 P(GPa) 0.07
0.86 0.14 13.7 12.5 0.0 LaO 0.86 F 0.14 FeAs χ (emu/cm 3 ) -0.1 P(GPa) 0 0.66 0.65 0 8 10 12 T(K) 14 16 0.14
0.86 0.14
+ ) 3 4 4 5 5 6
13 12 K/GPa 0. 30(1) K/GPa 2 2' T C (K) 12 1 1' 9' 8' 10' 6', 7' 6, 7 5' 4' 11' 3' 3 4 5 12', 13' LaO 0.86 F 0.14 FeAs 0.0 0.5 P(GPa) 0.14
0 0
4 EuFe 2 As 2 χ'(emu/mol) 2 T N 0 0.44 0.74 3 2 P(GPa) 1 0 10 20 30 T(K) 40 50
T c C
EuFe 1.715 Co 0.285 As 2 8 0.69 χ'(emu/mol) 0 0.52 0.38 4 P(GPa) T C 2 3 4 0 10 20 T(K) 30 1
21 2 T (K) C,N 20 2.4(1) K/GPa 3 EuFe 2 As 1.4 P 0.6 19 18 1 4 1, 4 1' 0.35(3) K/GPa 2.0(1) K/GPa 4' 3 3' EuFe 1.715 Co 0.285 As 2 2' 2 EuFe 2 As 2 5' 0.0 0.5 1.0 P(GPa)
μm μm 200 μm 70 μm 100 μm 30 40 μm
60 χ' (nv) 6 EuFe 2 As 2 P = 0 GPa χ' (nv) 40 20 16 20 24 T (K) 0-6 16 20 T (K) 24 28 200 μm
μm μm
0.285 0.8
T c 14
μm μm 2 T c μm