Magnetic Heads For High Density Recording

Single-molecule magnetic tweezers to probe the equilibrium dynamics of individual proteins at physiologically relevant forces and timescales

“…Although more elaborate force vs. MP expressions have been proposed, for instance involving double exponential corrections 72 , our empirical law provides a good prediction of the applied force over the explored range (1-120 pN). In the case of the tape head, there is an analytical expression for the magnetic field generated by the tape head as a function of the distance and electric current (Karlqvist field) 73 ; this allowed us to derive an analytical expression for the pulling force as a function of the electric current (at a given tape head-bead distance), which shows a quadratic dependence. Both expressions involve two fitting parameters ( Eqs.…”