Understanding Neodymium Magnets

  The Curie temperature is an exceptionally critical factor to consider when utilizing or contemplating the use of a magnet. Named after Pierre Curie, a French physicist and chemist, the Curie temperature quantifies the maximum temperature a specific type of magnet can endure before suffering a permanent loss of its magnetic properties, resulting in demagnetization. Normally, magnetic dipoles maintain alignment. However, when the Curie temperature is exceeded, these dipoles can become misaligned and consequently render the magnet functionally ineffective.

Each magnet type possesses a distinct Curie temperature, ranging from Neodymium at the lower end of the spectrum to Samarium cobalt at the higher end.

Neodymium (Rare Earth) Magnets

Neodymium, also known as Rare Earth magnets, represents the most prevalent type of magnet for household applications and do-it-yourself projects. With a Curie rating typically spanning 310–400 °C, Neodymium magnets may commence losing their magnetism at approximately 80 °C. When employing Neodymium magnets, monitoring the ambient temperature and humidity is advisable. Nonetheless, under most standard conditions, Neodymium magnets exhibit high reliability and sustain their magnetic properties effectively.

Strontium Ferrite Magnets

Strontium Ferrite magnets, also referred to as Ceramic magnets, possess a Curie temperature of approximately 480 °C. Surpassing Neodymium on the temperature scale, Ceramic magnets are suitable for applications situated in environments where humidity, temperature, or moisture content are elevated beyond the recommended levels for rare earth magnets. Ceramic magnets also feature a completely rust-proof design, making them optimal for wet conditions.

Alnico Magnets

Alnico is an acronym denoting a family of iron-based magnet alloys that additionally incorporate aluminum (Al), nickel (Ni), and cobalt (Co)—hence, al-ni-co. Positioned at the upper limit of the Curie scale, Alnico magnets exhibit a range of approximately 860 °C to 1,580 °C. These magnets are well-suited for applications demanding exceptionally high temperatures, even for prolonged durations, and are frequently observed in large-scale industrial contexts.

Magnet Grades and Temperature

The magnet grading system employs the letter 'N', followed by a numeral, to denote the overall strength of the magnet, measured in megagauss-oersteds (MGOe). In certain instances, an additional letter may succeed the grade, specifying the magnet's maximum operating temperature.

• M (Medium): Up to 100°C (212°F)

• H (High): Up to 120°C (248°F)

• SH (Super High): Up to 150°C (302°F)

• UH (Ultra High): Up to 180°C (356°F)

• EH (Extra High): Up to 200°C (392°F)

For example, an N42 3/16 in cube is rated for temperatures up to 80°C. In contrast, an N42SH 3/16 in cube is rated for temperatures up to 150°C.