John Van Vleck, winner of the 1977 Nobel Prize in Physics and Hollis Professor of Mathematics and Natural Philosophy emeritus, died in his sleep yesterday morning in Cambridge. He was 81 years old.

Described by his longtime colleague Edward M. Purcell, Gade University Professor, as "a very great and very much loved friend," Van Vleck is best known for creating the modern theory of quantum magnetism based on quantum mechanics.

The Swedish Academy of Sciences hailed him as "the father of modern magnetics" in 1977, when he won the Nobel Prize for research done mostly in the 1930s.

Born in Middletown, Connecticut, Van Vleck grew up in Wisconsin, where his father was a professor of mathematics at the University of Wisconsin.

He earned his master's (1921) and doctorate (1922) at Harvard, and taught here from 1922-1923. Returning as an associate professor in 1934, he became a full professor the following year and in 1951 assumed the Hollis professorship, the oldest endowed chair of science in North America.

He served as the first dean of the Division of Engineering and Applied Physics, which he was instrumental in creating, from 1951-57.

Purcell, who was a student of Van Vleck's in the 1930s at Harvard, said yesterday he was "extremely friendly--he treated us all as equals, when we were students and later."

Van Vleck leaves his wife, Abigail Pearson Van Vleck. Private funeral services will be held today. A Harvard memorial service will be announced