NFC reader long range antenna
In summary,

When using a NFC standard loop coil antenna, sized about 4x4 cm, the theoretical maximum working distance is 20 cm. In practice, the range for reliable communication is much smaller, usually about 5 cm (4 times smaller).

How could you improve the range without tweaking the power level and sensitivity of the NFC devices (master/transponder and slave/tag),

If you analyze the underlying physical equations, for the case of a circular loop coil antenna, the near field range (suitable for NFC communications) is about 1.414 times the radius of the circular coil. Check the link below to see the details,
https://physics.stackexchange.com/questions/44037/why-is-near-field-communication-nfc-range-limited-to-about-20cm


Answering to your specific concern,

To achieve a practical 60 cm range, you may try to create a near field with a theoretical range several times bigger, for instance, 180-240 cm, for which you need a circular coil of about 2.5-3.4 meters in diameter.
You can also try a square shaped coil of equivalent area to the circular coil.

If you finally try, please, update or answer your own post and let us know about your findings.