Isotone

Two nuclides are isotones if they have the same neutron number "N", but different proton number "Z". For example, boron-12 and carbon-13 nuclei both contain 7 neutrons, and so are isotones. Similarly, 36S, 37Cl, 38Ar, 39K, and 40Ca nuclei are all isotones of 20 because they all contain 20 neutrons. Despite its similarity to the Greek for "same stretching", the term was formed by the German physicist K. Guggenheimer by changing the "p" in "isotope" from "p" for "proton" to "n" for "neutron".
The largest numbers of observationally stable nuclides exist for isotones 50 (five: 86Kr, 88Sr, 89Y, 90Zr, 92Mo) and 82 (six: 138Ba, 139La, 140Ce, 141Pr, 142Nd, 144Sm). Neutron numbers for which there are no stable isotones are 19, 21, 35, 39, 45, 61, 89, 115, 123, and 127 or more. In contrast, the proton numbers for which there are no stable isotopes are 43, 61, and 83 or more. This is related to nuclear magic numbers, the number of nucleons forming complete shells within the nucleus, e.g. 2, 8, 20, 28, 50, 82, and 126. No more than one stable nuclide has the same odd neutron number, except for 1 (2H and 3He), 5 (9Be and 10B), 7 (13C and 14N), 55 (97Mo and 99Ru), and 107 (179Hf and 180mTa). Odd neutron numbers for which there is a stable nuclide and a primordial radionuclide are 27 (50V), 65 (113Cd), 81 (138La), 85 (147Sm), and 105 (176Lu). Neutron numbers for which there are two primordial radionuclides are 88 (151Eu and 152Gd) and 112 (187Re and 190Pt).

Manganese monosilicide is a non-stoichiometric compound, meaning that the 1:1 Mn:Si composition, lattice constant and many other properties vary depending on the synthesis and processing history of the crystal. 
MnSi has a cubic crystal lattice with no inversion center; therefore its crystal structure is helical, with right-hand and left-hand chiralities.
At low temperatures and magnetic fields, the magnetic structure of MnSi can be described as a stack of ferromagnetically ordered layers lying parallel to the (111) crystallographic planes. The direction of magnetic moment varies from layer to layer by a small angle due to the antisymmetric exchange.
Upon cooling to temperatures below Tc = 29 K, MnSi changes from a paramagnetic into a ferromagnetic state; the transition temperature Tc decreases with increasing pressure, vanishing at 1.4 GPa. 
Electron spins in MnSi show dissimilar, yet regular spatial arrangements at different values of applied magnetic field. Those arrangements are named helical, skyrmion, conical, and regular ferromagnetic. They can be controlled not only by temperature and magnetic field, but also by electric current, and the current density required for manipulating skyrmions (~106 A/m2) is approximately one million times smaller than that needed for moving magnetic domains in traditional ferromagnets. As a result, skyrmions in MnSi have potential application in ultrahigh-density magnetic storage devices.
Synthesis.
Centimeter-scale single crystals of MnSi can be prepared by direct crystallization from the melt using the Bridgman, zone melting or Czochralski methods.