Q-carbon 

• Ferromagnetism: A 2018 article in Physical Review Materials theoretically investigated the intrinsic magnetism in Q-carbon. The study followed up on experimental reports from the time, which claimed that Q-carbon was a room-temperature ferromagnetic phase of carbon, potentially possessing a large magnetic moment (0.4μB0.4 mu sub cap B0.4𝜇𝐵/atom). The theoretical work was conducted to better understand the magnetic and structural characteristics of this amorphous form of carbon.
• Superconductivity: The same 2018 theoretical study noted that Q-carbon exhibits superconductivity when doped with boron. This is believed to be due to the high proportion (75%–85%) of sp3s p cubed𝑠𝑝3-hybridized carbon atoms in Q-carbon, a property not found in typical amorphous carbon.
• Hall effect: An earlier 2018 paper in ACS Applied Nano Materials described experiments on Q-carbon, reporting room-temperature ferromagnetism and an extraordinary Hall effect. The study used a range of techniques, including magnetic force microscopy (MFM) and SQUID magnetometry, to characterize the material and its properties. 

Heavy boron (B) doping 

• Superconducting properties: A key simulation study from May 2020, published in Physical Review Materials, focused on the effect of boron pairing on the stability of heavily boron-doped carbon. The simulations considered different allotropes with high boron concentrations (up to 25%) to understand their energetic stability. The findings indicated that boron pairing had a relatively small effect on the overall energetic stability.
  
• Electrocatalytic activity: Though slightly outside the 2018–2020 window, related work in 2021 and later demonstrated the positive effect of heavy boron doping on the electrocatalytic properties of carbon-based materials, including enhanced oxygen reduction reactions for producing hydrogen peroxide. These studies often combine experimental synthesis with Density Functional Theory (DFT) calculations to understand the role of boron in modifying the electronic structure. 

Magnetism in carbon 

• Intrinsic magnetism: Beyond the specific properties of Q-carbon, the 2018 theoretical paper in Physical Review Materials explored the general mechanisms for magnetism in amorphous carbon. This work contributed to the understanding of how magnetic moments and structural characteristics arise in disordered carbon systems.
  
• Magnetic composite materials: Research during this period also explored magnetism by combining carbon with other magnetic materials. A December 2018 paper discussed the development of magnetic carbon nanofibers by co-doping with boron and decorating with MnCo alloy nanoparticles for use in supercapacitors. Micromagnetic simulations were used in later work to analyze the magnetic properties of these composites.