More frustration from the scientific community.
Bad Science and Room Temperature Superconductors - Sixty Symbols - Professor Philip Moriarty takes issue with a paper by scientists claiming to achieve room temperature superconductivity. Yesterday.
"LK-99 isn’t a superconductor — how science sleuths solved the mystery"
https://www.nature.com/articles/d41586-023-02585-7
Have I mentioned, that the "Dr." in my nickname originates from my 1994 PhD thesis:
"Measurement of the AC-Susceptibility and its Higher Harmonics on High Temperature Superconductors"
So that outcome is highly satisfying, because other than Prof. Moriarty, I'm obviously a 'Senior Expert'
on this science area, and I finally found an application for my unused expertise.
I found these documents fishy for the exact same arguments like him, i.e. bad scientific style (an aggressive claim) and mediocre / incomplete measurements.
In this Nature article the decisive magnetic measurements are not well appreciated, which would outscore the meaningless levitation videos.
In the paper from Max-Planck Institute,
https://arxiv.org/pdf/2308.06256, they substract the diamagnetic effect of copper from their DC-SQUID measurements.
What's left over is naught superconductivity, but a weak ferromagnetic behavior, maybe with a diamagnetic background, which both can explain the levitation effect.
Frank
PS: As we're still @ eevblog, I'd like to share a picture of my Hartshorn Bridge coils from way back when.. for those AC-Susceptibility measurements.
The leftmost coil has two secondary windings of 523 turns of 40 or 50µm wires in the small chambers, and a long primary wound over them, consisting of 1685 windings of 80µm wire.
An example of a complete coil assembly is on the right side. The Hartshorn Bridge (on an epoxy bobbin) is attached to a non-magnetic steel cylinder.
A calibrated temperature diode is attached at the lengthwise location of the sample, which is fixed inside the borehole of the bobbin.