Thank you for contacting Cypress Semiconductor.
Upon going through the datasheet of MX25R6435FZNIL0 (https://www.macronix.com/Lists/Datasheet/Attachments/7428/MX25R6435F,%20Wide%20Range,%2064Mb,%20v1.4.pdf ) I see it has option for Vcc = 1.65V to 3.6V. Please correct me if I am wrong.
Cypress has Serial NOR Flash devices both in Vcc = 2.7V to 3.6V range and Vcc = 1.7V to 2.0V range. Could you please let me know the operating voltage range of your application?
S25FL064L SPI Flash Memory works in Vcc = 2.7V to 3.6V range.
Datasheet link - https://www.cypress.com/file/316661/download
S25FS064S SPI Flash Memory works in Vcc = 1.7V to 2.0V range.
Datasheet link - https://www.cypress.com/file/338181/download