Ferrite bead for use for filtering a microSD card's Vcc
The bead is meant to absorb high-frequency noise currents (and dissipate it as heat) to maintain adequate high-frequency separation between shared power rails. 
There is a common type of ferrite beads that are designed to do exactly that. These beads have high impedance over wide high-frequency bands (low-pass filters).

Typical parameters are
- DC resistance -> should be as low as possible
- rated current -> requirements obviously depend on the load
- impedance characteristics curve -> depends on what kind of noise you primarily want to suppress  

Look at the parameters of this ferrite bead for example:



This would actually be a good choice for your design. It has a low DC resistance of 0.8 Ohm (minor losses) and is rated for 200mA. The average microSD shouldn't require more than 100mA (but look at the data sheet to be sure).



This shows impedance VS frequency. High-frequency noise, especially in the range from about 7MHz-3000MHz, will be absorbed.