  Josephson diodes (JDs) offer a promising route towards realizing
dissipation-less rectification at low temperatures. To be practically viable, a
JD must operate at zero magnetic fields, exhibit high operating frequencies and
efficiency, and possess tunability and scalability. In this study, we propose
and experimentally demonstrate a straightforward mechanism that encompasses all
these crucial features. Our approach involves utilizing an asymmetric Josephson
junction with a magnetic weak link to attain a diode effect in the switching
current. We substantiate this concept experimentally through the fabrication of
mesa-type sputter-deposited tri-layered ferromagnetic long NbN/GdN/NbN
Josephson junctions (JJs) in cross geometry. A robust zero-field diode effect
is observed with an efficiency boost of up to 40% achievable through
modification of the micromagnetic structure of the barrier. Notably, these
diodes maintain high efficiency across a wide temperature range, from the
lowest temperatures up to at least 4.2K, and exhibit an operating frequency of
nearly 28GHz.
