Table 1.

Cantilever Parameters^a

			cantilever
parameter	symbol	unit	A	B
frequency	$f_0$	Hz	7280	6550
spring constant	$k_0$	${\text{mN m}}^{-1}$	0.8	1.0
quality factor	$Q$	$\times {10}^4$	2.4	7.0
dissipation const.	$\text{Γ}$	${\text{pN s m}}^{-1}$	1.5	0.52
force noise	$\sqrt{P_{\delta F}}$	$\text{aN}/\sqrt{\text{Hz}}$	18	11
magnet thickness	$l_x$	nm	100	80
magnet width	$l_y$	nm	70	135
magnetic length	$l_z$	nm	1500	1500
sample thickness	$t$	nm	470	200

^aMagnet dimensions are indexed with respect to the $(x,y,z)$ coordinates defined in Figure 1. Magnetometry measurements were used to confirm the spring constants of cantilevers A and B (see Tables S2 and S3).