Magnetic recording media and methods and apparatus for identifying substrates suitable for magnetic recording media

A method of identifying a substrate suitable for use within a magnetic medium of a data storage device configured for magnetic recording, comprising:

• determining a plurality of first waviness values representative of surface waviness of a surface of a substrate within a first wavelength range, at a plurality of locations, respectively, on the surface;
• determining a plurality of second waviness values representative of surface waviness of the surface of the substrate within a second wavelength range, at the plurality of locations, respectively, the second wavelength range being different from the first wavelength range;
• calculating a plurality of composite waviness values respectively for the plurality of locations based on a combination of the plurality of first waviness values and the plurality of second waviness values;
• and
• determining to utilize the substrate for the magnetic medium in response to satisfying each of one or more conditions associated with the plurality of composite waviness values,
• wherein the one or more conditions comprises:
• each of the plurality of composite waviness values being less than a composite waviness threshold.

A method of identifying a substrate suitable for use within a magnetic medium of a data storage device configured for magnetic recording, comprising:

• determining a plurality of first waviness values representative of surface waviness of a surface of a substrate within a first wavelength range, at a plurality of locations, respectively, on the surface;
• determining a plurality of second waviness values representative of surface waviness of the surface of the substrate within a second wavelength range, at the plurality of locations, respectively, the second wavelength range being different from the first wavelength range;
• calculating a plurality of composite waviness values respectively for the plurality of locations based on the plurality of first waviness values and the plurality of second waviness values;
• calculating an average and a standard deviation based on the plurality of composite waviness values;
• generating a first set of simulated composite waviness values based on the average and the standard deviation and based on a statistical distribution, the statistical distribution being either a Gaussian distribution or a Weibull distribution;
• generating a second set of simulated composite waviness values based on the average and the standard deviation and based on the statistical distribution;
• calculating a plurality of simulated difference values by calculating differences between the first set of simulated composite waviness values and the second set of simulated composite waviness values, respectively;
• and
• determining to utilize the substrate for the magnetic medium in response to satisfying each of one or more conditions associated with the plurality of composite waviness values,
• wherein the one or more conditions comprise at least one of:
• a portion of the plurality of simulated difference values with a value less than a first simulated difference threshold being more than 95% of a number of the plurality of simulated difference values, or
• a portion of the plurality of simulated difference values with a value less than a second simulated difference threshold being more than 99% of a number of the plurality of simulated difference values.

A method for identifying a substrate suitable for use within a magnetic recording medium, the method comprising:

• determining a plurality of first waviness values representative of surface waviness of a surface of a substrate within a first wavelength range;
• determining a plurality of second waviness values representative of surface waviness of the surface of the substrate within a second, different wavelength range;
• combining the plurality of first waviness values and the plurality of second waviness values into a plurality of composite waviness values;
• determining whether the plurality of composite waviness values are less than a composite waviness threshold;
• and
• selecting the substrate for use within a magnetic recording medium in response to a determination that the plurality of composite waviness values are less than the composite waviness threshold;
• and
• rejecting the substrate in response to a determination that the plurality of composite waviness values are greater than or equal to the composite waviness threshold.