The phrase "are characterized not only" is correct and usable in written English.
It can be used when describing features or qualities of something, indicating that there are multiple characteristics to consider.
Example: "The species are characterized not only by their vibrant colors but also by their unique mating rituals."
Alternatives: "are defined not only" or "are distinguished not only".
All are characterized not only by generous welfare and maternal leave provisions, and infant care systems, but also by high levels of sexual equality as measured by incomes and social position.
Cells of hepatocellular cancer are characterized not only by altered structure, but also by pathological metabolism.
At the same time, open-pit dump trucks of different producers are characterized not only by the price but also by the design features, including overall dimensions.
Untreated patients with congenital growth hormone deficiency (GHD) and IGF-I deficiency are characterized not only by dwarfism but also by acromicria and organomicria, such as the heart.
Modern software-intensive systems are characterized not only by the movement of data, as has been the case in traditional distributed systems, but also by the movement of users, devices, and code.
Intensive Care Units (ICU) are characterized not only for caring the sickest patients but also due to its high levels of anxiety and stress in health workers, which takes its maximum expression in the burnout syndrome.
The interconnecting network of capillaries into which the arterioles empty is characterized not only by microscopic size but also by extremely thin walls only one cell thick.
We are about to enter the land of the Trump Administration, which is likely to be characterized not only by a lack of transparency, in the closed-door sense, but by outright lies.
The earliest settlements were characterized not only by the domestication of barley and sometimes wheat but also by the absence of pottery and of domestic animals other than the dog.
Psychologists have long recognized the Duchenne smile (named for the French neurologist Guillaume-Benjamin-Amand Duchenne [1806 75]), a sincere and spontaneous smile that is characterized not only by the stretching of the mouth but also by the elevation of the cheeks and the distinctive contraction of the muscles around the eye.
Each mode, however, is characterized not only by its finalis but also by a unique recitation tone, tenor or confinalis the upper fifth for authentic modes and the third for plagal (except where other considerations, such as the avoidance of intonation problems, prevail).
