This document summarizes research on improving the magnetic and electrical properties of type-II superconductors through nanostructured hybrids. It discusses using nanostructured defects like dots of materials like nickel to enhance pinning of vortices in the mixed state and reduce resistance. Arrays of magnetic dots on niobium films allow controlling the remanent magnetic state of the dots to realize three-state memory function and ratchet effects influencing voltage outputs. The compensation field and matching fields where resistance is minimized depend on sample design.

1. J. L. Vicent
Departamento Fisica de Materiales
Facultad Ciencias Físicas
Universidad Complutense
28040 Madrid (Spain)
IMDEA-Nanociencia
28049 Madrid (Spain)
Grupo de Magnetismo y Nanolitografía-UCM
4. Mejora de las propiedades magnéticas y eléctricas de los
superconductores mediante la fabricación de nanoestructuras híbridas

2. Type II Supercondutors
Vortices
Mixed State
Tc
Mixed
State
Normal
State
Meissner
State
Hc2
Hc1
NbSe2
Hess et al. PRL62,214 (1989)
Abrikosov Lattice
Hc1<H<Hc2
Mixed State
Vortices
on the
move ?

3. 
 vBE
Magnetic Field
VDC
R(H)

B
B
0
Current Density

J

 oL JF 

v
J
E
FL ,v
Vortices move  J

Bc1<B<Bc2
Mixed State
Vortex motion causes energy
dissipation:
Resistance ≠ 0
&

4. Magnetic pinning
Local depression of the
superconductivity
Core pinning
r2
Js

ns(r)
H
0=h/2e=2.067×10-15 Wb
Superconducting energy is
minimized by locating
vortices in defects
PINNING MECHANISMSVortex structure
sketch

5. Pinning center
Minimum of
potential
Pinning Force Fp
Decrease vortex
velocity
Minimum in
Resistance
0 FL
Fp
V(x)
R
-4
-3
-2
-1 1
2
3
4
5-5
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6
10
-5
10
-4
10
-3
10
-2
10
-1
10
0
R()
H(kOe)
Superconductor
Defect
Película de Nb
Array dots
Si
100
nm

6. -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6
10
-5
10
-4
10
-3
10
-2
10
-1
10
0
R()
H(kOe)
Rectangular lattice
a=400nm b=600nm
ΔH = 85.3 Oe
a
b
S
0
0
0
0
axb
n
Hn
0

Minima in Resistance
Vortex density =n· Pinning center density
-4
-3
-2
-1 1
2
3
4
5-5
0n
S
n
B Matching Fields
Vortex lattice u.c. areaS
n = Vortices per u.c.
0.99Tc 100 mA
100 nm Nb + 40 nm Ni dots

7. Superconductor Nb
Defectos: Cu, Si, Ni, Co, Py,
a-NdCo5, Co/Pd (multicapas)

8. Magnetism enhances superconductivity
Field induced superconductivity
V AV
Lange, van Bael, Bruynseraede,Moshchalkov PRL 90 (2003)
H=0
H0
SC SC
Superconductor
Superconductor
Magnets with out of plane Mz
Magnets with out of plane Mz

9. Dot
Co/Pd
Nb
-0.4 -0.2 0.0 0.2 0.4
10
-3
10
-2
10
-1
10
0
10 mA
20 mA
50 mA
100 mA
R()
H (kOe)
-2 -1 0 1 2
10
-4
10
-3
10
-2
10
-1
10
0
Desimanado
Imanado
R/RN
H/Hmatching
Dot Si
Nb

10. -0,4 -0,3 -0,2 -0,1 0,0 0,1 0,2 0,3 0,4
10
-5
10
-4
10
-3
10
-2
10
-1
10
0
+Msat
-Msat
R()
H(kOe)
Pinning en N= -1 para distintas
memorias magneticas de los dots
2.5 mA
T=0.99Tc
Tc=8.385 K
Array of Ni dots (400 nm x 400 nm) /Nb film
+1
-1
Dot Ni
Nb Nb Nb

11. -0.15 -0.10 -0.05 0.00 0.05 0.10 0.15
0.0
1.0x10
-3
2.0x10
-3
3.0x10
-3
Desde -3 kOe
Desde -1 kOe
Desde -0.4 kOe
Desde -0.3 kOe
Desde -0.25 kOe
Desde 2 kOe
Desde 0.8 kOe
Desde 0.5 kOe
Desde 0.35 kOe
Desde 0.25 kOe
R()
H(kOe)
Pinning en N= -1 para distintas
memorias magneticas de los dots
2.5 mA
T=0.99Tc
Tc=8.385 K
Dot Ni
Nb Nb Nb
-0,4 -0,3 -0,2 -0,1 0,0 0,1 0,2 0,3 0,4
10
-5
10
-4
10
-3
10
-2
10
-1
10
0
+Msat
-Msat
R()
H(kOe)
Pinning en N= -1 para distintas
memorias magneticas de los dots
2.5 mA
T=0.99Tc
Tc=8.385 K

12. Three-state memory nanodevice:
+1 (M =+Mz); 0 (M = 0); -1 (M =-Mz);
Reading nanodevice:
Zero output signal (VDC = 0)
for specific value of Happl
which depends on how the
device is built.
Happl.= 0
Happl.≠ 0
Input signals: ac currents
Output signals: dc voltages
Nb/(Co/Pd)

13. -1,0 -0,5 0,0 0,5 1,0
-20
-10
0
10
20
Vdc,max(mV)
MR / MS
1 2 3 4 5 6
-20
-10
0
10
20
V
dc
(mV)
I
ac
(mA)
MR/MS = 0.65
- Vdc, max
+Vdc, max
del Valle et al. Sci. Rep. (2015)
+1
0
-1
T = 0.99Tc
Remanent magnetic states control ratchet effects

14. 8.40 8.42 8.44 8.46 8.48 8.50 8.52
0
100
200
300
400
500
T(K)
H(Oe)
R / RN
0.0 0.5 1.0
Hcompensation = 240 Oe
Hmatching= 36 Oe
A
C
B
C
B
A
Hcompensation and Hmatching depend on the
sample design.
Happl

15. R / RN
0.0 0.5 1.0
8,42 8,44 8,46 8,48 8,50 8,52
0
100
200
300
400
500
T(K)
H(Oe)
0 100 200 300 400
-20
-10
0
10
20
Vdc,max(mV)
H (Oe)
-1,0 -0,5 0,0 0,5 1,0
-20
-10
0
10
20
Vdc,max(mV)
MR / MS
+1
0
-1
Happl = 0
Closing….

16. AAlicia Gomez
Javier
del V
Javier del Valle
JaviEer
del VElvira Gonzalez

17. The
END