scholarly journals Coherent emission from the stack of Josephson junctions with the non-uniform inductive interaction

During last decade, considerable efforts were made to achieve coherent emission from stacks of many Josephson junctions. It is known that strong emission from a junction in the presence of external magnetic field appears at the so-called Fiske steps in the IV-characteristic at voltages which correspond to frequencies of geometrical resonances. However, it is possible to obtain resonant steps in long junctions without external magnetic field. The periodical movement of fluxons is excited due to some disorder in the distribution of critical currents along junctions. The so-called zero-field steps are formed in the IV-curve due to the interaction of fluxons with oscillations of voltage at Josephson frequencies. We investigated numerically IV-characteristics and the dependence of the average square of ac voltage at the end of the stack of two long Josephson junctions on the average voltage. Junctions interacted inductively with each other. We introduced not only the Gaussian distribution of critical currents along junctions but also the Gaussian distribution of coefficients of the interaction between junctions (mutual inductances). Zero-field steps in the IV-characteristic were found at voltages which corresponded to frequencies of in-phase collective modes in the stack as well as to frequencies of uncoupled junctions. Zero-field steps appeared in the hysteretic region of the IV-curve. There appeared also jumps of voltage from the resistive branch to the zero-field step. We showed that there existed distributions of mutual inductances along junctions which provided jumps to voltages at which the average square of ac voltage at the end of the stack (which is proportional to power of emission) was larger than that for the stack with the uniform distribution of mutual inductances.

2015 ◽  
Vol 233-234 ◽  
pp. 741-744
Author(s):  
Sergey Mikhailovich Podgornykh

Effect of the magnetic prehistory on the temperature dependence of the heat capacity of the superconducting Pb, La, Sn. has been studied. As soon as the external magnetic field riches the valueHext=HCthe superconductivity is completely destroyed. The trapped flux was produced in the ring specimen after the magnetic field was turned off atT<TC. We observed a difference of the value of the heat capacity between zero field cooled (ZFC) and field cooled (FC) states in zero magnetic field for the ring specimen. It is found that the FC heat capacity is smaller than the heat capacity both in the normal and in superconducting states.


1977 ◽  
Vol 55 (12) ◽  
pp. 1066-1073 ◽  
Author(s):  
C. di Lauro ◽  
E. Perri

The Zeeman band profiles are calculated for near-case (b) triplet–singlet transitions in asymmetric rotors, making allowance for the intensity perturbations induced by an external magnetic field. It is shown that new bands correlating with zero-field forbidden lines can be observed under the effect of sufficiently high fields. Band profiles and the patterns of the magnetic sublevels of the triplet state split by the external field are discussed in detail for the Paschen–Back limit.


2021 ◽  
Vol 50 (10) ◽  
pp. 3468-3472
Author(s):  
Roman Boča ◽  
Ján Titiš ◽  
Cyril Rajnák ◽  
J. Krzystek

Magnetochemical standard HgCo(NCS)4 with positive zero-field splitting parameter D displays a slow magnetic relaxation strongly dependent upon the external magnetic field.


1997 ◽  
Vol 81 (3) ◽  
pp. 1335-1340 ◽  
Author(s):  
I. V. Vernik ◽  
S. Keil ◽  
N. Thyssen ◽  
T. Doderer ◽  
A. V. Ustinov ◽  
...  

We investigated numerically IV-characteristics and power of emission from stacks with various quantities of long Josephson junctions (up to 6 junctions) which interacted inductively with each other. Parameters of junctions were chosen close to those for MoRe-Si(W)-MoRe heterostructures. We set Gaussian spread of about 0.01% of critical currents along junctions. Electrical properties of a stack consisted of three junctions was investigated in details. Zero-fi eld steps at voltages corresponding to frequencies of various modes of electromagnetic waves in the stack were found in the IV-characteristic. We showed that positions of zero-fi eld steps in IV-curves were in good agreement with predictions of the theory. The highest maximum of power of emission corresponded to the so-called in-phase mode at which all voltages over junctions in the stack oscillate in-phase. Considering stacks with many junctions, we showed that power of emission at the voltage of the resonance which corresponds to the in-phase mode is proportional to the square of quantity of long junctions in the stack that is the characteristic of coherent emission.


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